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  • I'm an ocean microbiologist at the University of Tennessee,

  • and I want to tell you guys about some microbes

  • that are so strange and wonderful

  • that they're challenging our assumptions about what life is like on Earth.

  • So I have a question.

  • Please raise your hand if you've ever thought it would be cool

  • to go to the bottom of the ocean in a submarine?

  • Yes.

  • Most of you, because the oceans are so cool.

  • Alright, now -- please raise your hand

  • if the reason you raised your hand to go to the bottom of the ocean

  • is because it would get you a little bit closer

  • to that exciting mud that's down there.

  • (Laughter)

  • Nobody.

  • I'm the only one in this room.

  • Well, I think about this all the time.

  • I spend most of my waking hours

  • trying to determine how deep we can go into the Earth

  • and still find something, anything, that's alive,

  • because we still don't know the answer to this very basic question

  • about life on Earth.

  • So in the 1980s, a scientist named John Parkes, in the UK,

  • was similarly obsessed,

  • and he came up with a crazy idea.

  • He believed that there was a vast, deep, and living microbial biosphere

  • underneath all the world's oceans

  • that extends hundreds of meters into the seafloor,

  • which is cool,

  • but the only problem is that nobody believed him,

  • and the reason that nobody believed him

  • is that ocean sediments may be the most boring place on Earth.

  • (Laughter)

  • There's no sunlight, there's no oxygen,

  • and perhaps worst of all,

  • there's no fresh food deliveries for literally millions of years.

  • You don't have to have a PhD in biology

  • to know that that is a bad place to go looking for life.

  • (Laughter)

  • But in 2002, [Steven D'Hondt] had convinced enough people

  • that he was on to something that he actually got an expedition

  • on this drillship, called the JOIDES Resolution.

  • And he ran it along with Bo Barkerrgensen of Denmark.

  • And so they were finally able to get

  • good pristine deep subsurface samples

  • some really without contamination from surface microbes.

  • This drill ship is capable of drilling thousands of meters underneath the ocean,

  • and the mud comes up in sequential cores, one after the other --

  • long, long cores that look like this.

  • This is being carried by scientists such as myself who go on these ships,

  • and we process the cores on the ships and then we send them home

  • to our home laboratories for further study.

  • So when John and his colleagues

  • got these first precious deep-sea pristine samples,

  • they put them under the microscope,

  • and they saw images that looked pretty much like this,

  • which is actually taken from a more recent expedition

  • by my PhD student, Joy Buongiorno.

  • You can see the hazy stuff in the background.

  • That's mud. That's deep-sea ocean mud,

  • and the bright green dots stained with the green fluorescent dye

  • are real, living microbes.

  • Now I've got to tell you something really tragic about microbes.

  • They all look the same under a microscope,

  • I mean, to a first approximation.

  • You can take the most fascinating organisms in the world,

  • like a microbe that literally breathes uranium,

  • and another one that makes rocket fuel,

  • mix them up with some ocean mud,

  • put them underneath a microscope,

  • and they're just little dots.

  • It's really annoying.

  • So we can't use their looks to tell them apart.

  • We have to use DNA, like a fingerprint,

  • to say who is who.

  • And I'll teach you guys how to do it right now.

  • So I made up some data, and I'm going to show you some data that are not real.

  • This is to illustrate what it would look like

  • if a bunch of species were not related to each other at all.

  • So you can see each species

  • has a list of combinations of A, G, C and T,

  • which are the four sub-units of DNA,

  • sort of randomly jumbled, and nothing looks like anything else,

  • and these species are totally unrelated to each other.

  • But this is what real DNA looks like,

  • from a gene that these species happen to share.

  • Everything lines up nearly perfectly.

  • The chances of getting so many of those vertical columns

  • where every species has a C or every species has a T,

  • by random chance, are infinitesimal.

  • So we know that all those species had to have had a common ancestor.

  • They're all relatives of each other.

  • So now I'll tell you who they are.

  • The top two are us and chimpanzees,

  • which y'all already knew were related, because, I mean, obviously.

  • (Laughter)

  • But we're also related to things that we don't look like,

  • like pine trees and Giardia, which is that gastrointestinal disease

  • you can get if you don't filter your water while you're hiking.

  • We're also related to bacteria like E. coli and Clostridium difficile,

  • which is a horrible, opportunistic pathogen that kills lots of people.

  • But there's of course good microbes too, like Dehalococcoides ethenogenes,

  • which cleans up our industrial waste for us.

  • So if I take these DNA sequences,

  • and then I use them, the similarities and differences between them,

  • to make a family tree for all of us

  • so you can see who is closely related,

  • then this is what it looks like.

  • So you can see clearly, at a glance,

  • that things like us and Giardia and bunnies and pine trees

  • are all, like, siblings,

  • and then the bacteria are like our ancient cousins.

  • But we're kin to every living thing on Earth.

  • So in my job, on a daily basis,

  • I get to produce scientific evidence against existential loneliness.

  • So when we got these first DNA sequences,

  • from the first cruise, of pristine samples from the deep subsurface,

  • we wanted to know where they were.

  • So the first thing that we discovered is that they were not aliens,

  • because we could get their DNA to line up with everything else on Earth.

  • But now check out where they go on our tree of life.

  • The first thing you'll notice is that there's a lot of them.

  • It wasn't just one little species

  • that managed to live in this horrible place.

  • It's kind of a lot of things.

  • And the second thing that you'll notice,

  • hopefully, is that they're not like anything we've ever seen before.

  • They are as different from each other

  • as they are from anything that we've known before

  • as we are from pine trees.

  • So John Parkes was completely correct.

  • He, and we, had discovered a completely new and highly diverse

  • microbial ecosystem on Earth

  • that no one even knew existed before the 1980s.

  • So now we were on a roll.

  • The next step was to grow these exotic species in a petri dish

  • so that we could do real experiments on them

  • like microbiologists are supposed to do.

  • But no matter what we fed them,

  • they refused to grow.

  • Even now, 15 years and many expeditions later,

  • no human has ever gotten a single one of these exotic deep subsurface microbes

  • to grow in a petri dish.

  • And it's not for lack of trying.

  • That may sound disappointing,

  • but I actually find it exhilarating,

  • because it means there are so many tantalizing unknowns to work on.

  • Like, my colleagues and I got what we thought was a really great idea.

  • We were going to read their genes like a recipe book,

  • find out what it was they wanted to eat and put it in their petri dishes,

  • and then they would grow and be happy.

  • But when we looked at their genes,

  • it turns out that what they wanted to eat was the food we were already feeding them.

  • So that was a total wash.

  • There was something else that they wanted in their petri dishes

  • that we were just not giving them.

  • So by combining measurements from many different places

  • around the world,

  • my colleagues at the University of Southern California,

  • Doug LaRowe and Jan Amend,

  • were able to calculate that each one of these deep-sea microbial cells

  • requires only one zeptowatt of power,

  • and before you get your phones out, a zepto is 10 to the minus 21,

  • because I know I would want to look that up.

  • Humans, on the other hand,

  • require about 100 watts of power.

  • So 100 watts is basically if you take a pineapple

  • and drop it from about waist height to the ground 881,632 times a day.

  • If you did that and then linked it up to a turbine,

  • that would create enough power to make me happen for a day.

  • A zeptowatt, if you put it in similar terms,

  • is if you take just one grain of salt

  • and then you imagine a tiny, tiny, little ball

  • that is one thousandth of the mass of that one grain of salt

  • and then you drop it one nanometer,

  • which is a hundred times smaller than the wavelength of visible light,

  • once per day.

  • That's all it takes to make these microbes live.

  • That's less energy than we ever thought would be capable of supporting life,

  • but somehow, amazingly, beautifully,

  • it's enough.

  • So if these deep-subsurface microbes

  • have a very different relationship with energy than we previously thought,

  • then it follows that they'll have to have

  • a different relationship with time as well,

  • because when you live on such tiny energy gradients,

  • rapid growth is impossible.

  • If these things wanted to colonize our throats and make us sick,

  • they would get muscled out by fast-growing streptococcus

  • before they could even initiate cell division.

  • So that's why we never find them in our throats.

  • Perhaps the fact that the deep subsurface is so boring

  • is actually an asset to these microbes.

  • They never get washed out by a storm.

  • They never get overgrown by weeds.

  • All they have to do is exist.

  • Maybe that thing that we were missing in our petri dishes

  • was not food at all.

  • Maybe it wasn't a chemical.

  • Maybe the thing that they really want,

  • the nutrient that they want, is time.

  • But time is the one thing that I'll never be able to give them.

  • So even if I have a cell culture that I pass to my PhD students,

  • who pass it to their PhD students, and so on,

  • we'd have to do that for thousands of years

  • in order to mimic the exact conditions of the deep subsurface,

  • all without growing any contaminants.

  • It's just not possible.

  • But maybe in a way we already have grown them in our petri dishes.

  • Maybe they looked at all that food we offered them and said,

  • "Thanks, I'm going to speed up so much

  • that I'm going to make a new cell next century.

  • Ugh.

  • (Laughter)

  • So why is it that the rest of biology moves so fast?

  • Why does a cell die after a day

  • and a human dies after only a hundred years?

  • These seem like really arbitrarily short limits

  • when you think about the total amount of time in the universe.

  • But these are not arbitrary limits.

  • They're dictated by one simple thing,

  • and that thing is the Sun.

  • Once life figured out how to harness the energy of the Sun

  • through photosynthesis,

  • we all had to speed up and get on day and night cycles.

  • In that way, the Sun gave us both a reason to be fast

  • and the fuel to do it.

  • You can view most of life on Earth like a circulatory system,

  • and the Sun is our beating heart.

  • But the deep subsurface is like a circulatory system

  • that's completely disconnected from the Sun.

  • It's instead being driven by long, slow geological rhythms.

  • There's currently no theoretical limit on the lifespan of one single cell.

  • As long as there is at least a tiny energy gradient to exploit,

  • theoretically, a single cell could live

  • for hundreds of thousands of years or more,

  • simply by replacing broken parts over time.

  • To ask a microbe that lives like that to grow in our petri dishes

  • is to ask them to adapt to our frenetic, Sun-centric, fast way of living,

  • and maybe they've got better things to do than that.

  • (Laughter)

  • Imagine if we could figure out how they managed to do this.

  • What if it involves some cool, ultra-stable compounds