WEBVTT

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

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and I want to tell you guys
about some microbes

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that are so strange and wonderful

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

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So I have a question.

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

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

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Yes.

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Most of you, because
the oceans are so cool.

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Alright, now -- please raise your hand

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

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is because it would get you
a little bit closer

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to that exciting mud that's down there.

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(Laughter)

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Nobody.

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I'm the only one in this room.

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Well, I think about this all the time.

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I spend most of my waking hours

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trying to determine
how deep we can go into the Earth

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

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

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about life on Earth.

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

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was similarly obsessed,

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and he came up with a crazy idea.

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

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underneath all the world's oceans

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that extends hundreds of meters
into the seafloor,

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which is cool,

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but the only problem
is that nobody believed him,

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and the reason that nobody believed him

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

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(Laughter)

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

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and perhaps worst of all,

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

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You don't have to have a PhD in biology

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

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(Laughter)

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

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

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on this drillship,
called the JOIDES Resolution.

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And he ran it along with
Bo Barker Jørgensen of Denmark.

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And so they were finally able to get

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good pristine deep subsurface samples

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some really without contamination
from surface microbes.

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

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

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long, long cores that look like this.

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

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

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to our home laboratories
for further study.

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So when John and his colleagues

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got these first precious
deep-sea pristine samples,

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they put them under the microscope,

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and they saw images
that looked pretty much like this,

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which is actually taken
from a more recent expedition

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by my PhD student, Joy Buongiorno.

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You can see the hazy stuff
in the background.

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

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and the bright green dots
stained with the green fluorescent dye

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are real, living microbes.

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

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They all look the same under a microscope,

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I mean, to a first approximation.

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You can take the most fascinating
organisms in the world,

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like a microbe that literally
breathes uranium,

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and another one that makes rocket fuel,

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mix them up with some ocean mud,

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put them underneath a microscope,

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and they're just little dots.

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It's really annoying.

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

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We have to use DNA, like a fingerprint,

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to say who is who.

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

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

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This is to illustrate
what it would look like

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

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So you can see each species

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

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which are the four sub-units of DNA,

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

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and these species
are totally unrelated to each other.

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But this is what real DNA looks like,

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from a gene that these species
happen to share.

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Everything lines up nearly perfectly.

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The chances of getting
so many of those vertical columns

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

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by random chance, are infinitesimal.

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

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They're all relatives of each other.

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So now I'll tell you who they are.

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The top two are us and chimpanzees,

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

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(Laughter)

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

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like pine trees and Giardia,
which is that gastrointestinal disease

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

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

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

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

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which cleans up
our industrial waste for us.

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So if I take these DNA sequences,

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

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to make a family tree for all of us

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so you can see who is closely related,

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then this is what it looks like.

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So you can see clearly, at a glance,

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that things like us and Giardia
and bunnies and pine trees

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are all, like, siblings,

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and then the bacteria
are like our ancient cousins.

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

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So in my job, on a daily basis,

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I get to produce scientific evidence
against existential loneliness.

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So when we got these first DNA sequences,

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

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we wanted to know where they were.

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

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

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

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

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It wasn't just one little species

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that managed to live
in this horrible place.

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It's kind of a lot of things.

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And the second thing that you'll notice,

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

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They are as different from each other

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as they are from anything
that we've known before

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as we are from pine trees.

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So John Parkes was completely correct.

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

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microbial ecosystem on Earth

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that no one even knew existed
before the 1980s.

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So now we were on a roll.

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

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so that we could
do real experiments on them

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like microbiologists are supposed to do.

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But no matter what we fed them,

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they refused to grow.

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Even now, 15 years
and many expeditions later,

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

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to grow in a petri dish.

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And it's not for lack of trying.

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That may sound disappointing,

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but I actually find it exhilarating,

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

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

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

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

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and then they would grow and be happy.

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But when we looked at their genes,

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

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So that was a total wash.

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There was something else
that they wanted in their petri dishes

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that we were just not giving them.

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So by combining measurements
from many different places

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around the world,

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my colleagues at the University
of Southern California,

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Doug LaRowe and Jan Amend,

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

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requires only one zeptowatt of power,

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

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because I know I would want
to look that up.

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Humans, on the other hand,

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require about 100 watts of power.

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So 100 watts is basically
if you take a pineapple

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

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

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

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A zeptowatt, if you put it
in similar terms,

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is if you take just one grain of salt

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and then you imagine
a tiny, tiny, little ball

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

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and then you drop it one nanometer,

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

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once per day.

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

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

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but somehow, amazingly, beautifully,

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it's enough.

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So if these deep-subsurface microbes

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

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then it follows that they'll have to have

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a different relationship
with time as well,

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because when you live
on such tiny energy gradients,

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rapid growth is impossible.

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

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they would get muscled out
by fast-growing streptococcus

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before they could even
initiate cell division.

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

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Perhaps the fact that the deep
subsurface is so boring

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is actually an asset to these microbes.

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They never get washed out by a storm.

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They never get overgrown by weeds.

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All they have to do is exist.

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Maybe that thing that we were missing
in our petri dishes

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was not food at all.

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Maybe it wasn't a chemical.

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Maybe the thing that they really want,

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the nutrient that they want, is time.

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

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

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

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we'd have to do that
for thousands of years

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

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all without growing any contaminants.

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It's just not possible.

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

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

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

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

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Ugh.

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(Laughter)

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

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Why does a cell die after a day

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and a human dies
after only a hundred years?

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These seem like really
arbitrarily short limits

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

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But these are not arbitrary limits.

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They're dictated by one simple thing,

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and that thing is the Sun.

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

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through photosynthesis,

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

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

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and the fuel to do it.

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

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and the Sun is our beating heart.

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But the deep subsurface
is like a circulatory system

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that's completely
disconnected from the Sun.

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

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

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

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theoretically, a single cell could live

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for hundreds of thousands
of years or more,

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simply by replacing
broken parts over time.

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

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

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

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(Laughter)

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

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What if it involves some cool,
ultra-stable compounds

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that we could use
to increase the shelf life

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in biomedical or industrial applications?

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Or maybe if we figure out
the mechanism that they use

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to grow so extraordinarily slowly,

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we could mimic it in cancer cells
and slow runaway cell division.

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I don't know.

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I mean, honestly, that is all speculation,

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but the only thing I know for certain

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is that there are
a hundred billion billion billlion

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living microbial cells

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underlying all the world's oceans.

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That's 200 times more than the total
biomass of humans on this planet.

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And those microbes have
a fundamentally different relationship

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with time and energy than we do.

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What seems like a day to them

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might be a thousand years to us.

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They don't care about the Sun,

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and they don't care about growing fast,

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and they probably don't give a damn
about my petri dishes ...

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(Laughter)

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but if we can continue to find
creative ways to study them,

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then maybe we'll finally figure out
what life, all of life, is like on Earth.

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Thank you.

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(Applause)