I just need you to look at this. This
might be one of the most incredible
structures in all of biology. We're
flying over a near crystallin layer of
proteins protecting one of the most
extreme organisms on the planet. This is
DinoCus radioins, a hardcore bacteria
that's been in the news a lot lately for
being basically indestructible. For
real. Since its discovery back in the
50s, scientists have thrown basically
everything we can at samples of this
little fella. It's been blasted with
thousands of times a lethal dose of
ionizing radiation and survived. They
had a sample of this stuff live on the
outside of the International Space
Station for a full year. Totally fine.
And most recently, there's this paper
making the rounds where an especially
eager team from John's Hopkins
University exposed Dradio to enough
force to simulate an asteroid impact,
which this bacteria effectively shrugged
off. So, I mean, it's kind of hard not
to call this thing a bacterial
spaceship. But the closer we look at
this astounding little critter, the more
we find earth-based forces that would
push this kind of system to evolve. So
today, let's explore the incredible
biology that makes Dino Caucus radio one
of the most durable living things on the
planet. Let's get into it.
to check out our awesome sticker packs and molecular papercraft scenes. But for
now, let's pick apart this tank of a
bacteria. So yeah, Dinocus radiourons is
an incredibly wellstudied extreophile
bacteria. It was first discovered in the
' 50s when scientists in Oregon tried to
sterilize a sample of dog food with a
huge dose of gamma radiation which
draodan survived. Since then, this fella
has baffled the scientific community
with the ability to withstand thousands
of times the radiation dose that would
instantly kill a person. Hence the name
radio durable ants. Right, cool. And
here's the thing. Radiation resistance
was the focus of research into
draodurance for ages. So, a lot of what
we're going to see in this video is
focused on surviving Hulk level doses of
gamma rays. But draodurance is a
scavenger. It lives by landing on a pile
of trash, pumping out a bunch of
digestive enzymes, and slurping up the
nutrients that come back from that.
Surely, this bacteria didn't evolve the
ability to survive meteor impacts and
the vacuum of space just to find more
trash to eat, right? But we're going to
be able to put together a much cooler
picture of why radioons ended up this
way as we examine each individual
mechanism. In this video, we'll pick
apart a handful of the mechanisms
Dinocockus uses to stay alive no matter
what the universe throws at it. But
anyway, let's actually start exploring
what makes this bacteria so tough. This
is roughly what the average Dinocockus
radio cluster will look like. We've got
four of these little guys kind of
huddled together in this hairy little
blob. And usually you'll find them on a
pile of dead organic material where they
scavenge for food by pumping out
digestive enzymes and absorbing what
carbs and protein they can from their
environment. Like I said before,
draodurance is immediately striking
because instead of just an outer
membrane like other cells, they cover
themselves in this near crystallin
protein armor. This is the S layer of
dinoccus radiooderans and it is mainly
composed of one protein HPI. HPI is made
out of six little chains like this which
by the way are made out of egg-like
domains just like the main structural
component of the Titan protein in your
muscle. A full HPI unit is pumped out of
the draodan's membrane and six subunits
of this HPI armor will self assemble
into this sturdy looking snowflake
complex and a bunch of those complexes
will link up into this sheet that covers
the entire bacteria. And look at that.
They're little hexagons. Wild. I wonder
if that shape has any like special
mathematical significance or anything.
Anyway, this layer of hexagonally packed
intermediate protein also serves as an
anchor for long chains of sugars called
dopole. These form a kind of cell wall
for draoderans. Now, the exact structure
of dinopol has yet to be determined, but
researchers have proven that these
sugars provide some defense against
radiation as well as an antioxidant
buff. Even at their edges, draodurance
is going for maximum radiation
shielding. While this hexagon shell
looks incredible, it's also incredibly
expensive to make. What's more, this
shell doesn't seem to directly
contribute to radiation defense.
Instead, the S layer allows Draodurn to
hold its shape no matter what hits it,
even a meteor impact. And it also seems
to help defend against big temperature
swings. Sure, it serves as an anchor for
this radioactive sugar shield, but you
can find way cheaper methods to anchor a
cell wall to your membrane as a
bacteria. But yeah, that's a really
interesting distinction that may help us
understand what draodurance is actually
trying to survive later on. Keep that
information in your back pocket, I
guess. For now, we can find some direct
radiation defense just below the S layer
where we find these beefy pore
complexes. Just beneath the S layer are
these SDBC complexes embedded in the
outer membrane. These are where the
radiation defense gets kicked up a whole
new level. Right off the bat, these
three pores are studded with a powerful
antioxidant called dino xanthin, which
adds its own form of strong radiation
defense. And just a quick fun fact,
doanthin also contributes to making
draodurance a light pink color, which is
just neat. But moving on, just beneath
these pores are a trimer of an even
stronger antioxidant domain, which is a
super oxide dismutase, which provides an
even stronger radiation buff. Now, you
might be wondering why I keep describing
these as layer proteins as antioxidants
when I'm supposedly talking about
radiation defense. And trust me, the
connection between those two ideas is
going to blow your mind if you don't
already know it. But stick with me here.
We'll get to that connection once we
have a few more pieces of the radio's
puzzle. Going deeper, the SDBC complex
actually has this cool tail that extends
all the way down through Draodurance's
outer shell. This bacteria uses a
classic double membrane with just a ton
of pepidoglycin in between to hold its
shape with SDBC tethering the inner
membrane to the outer membrane. That
structural support is even stronger. All
in all, the S layer and anti-radiation
carbohydrate coat of draodurance provide
a great defense and a passive buff to
radiation damage. But in order to
survive the level of gamma rays that
dino radiodurans does, you're going to
need a lot of active counter measures as
well, which we're going to get to right
and subscribe today. And now we can get to the good stuff. So, we've seen the
great perimeter defenses employed by
D-raodderans, but now let's go to the
bacterial interior and see where the
real magic happens. If there's still
radiation getting through this S layer,
how does Dinocus radiodans mitigate that
damage? Cutting directly into one of
these little fellas gives part of the
game away instantly. Dinocus radio is
optimized for durability. While other
bacteria make a soupy mess of their DNA,
Draodurance organizes its DNA into this
Taurus, I mean donut shape. While this
nucleoid looks cool and it's fun to say
donut DNA, the circle structure isn't
the most important aspect here. It's
what radioodurance packages inside this
donut. Draodurance maintains multiple
copies of its genome and several
redundant copies of critical genes. More
importantly, those copies are
persistently linked by structures called
holiday junctions, which are involved in
a repair process called homologous
recombination, which means that even
when this bacteria gets blasted with a
ton of DNA cutting radiation, it can
cross reference one homologous
chromosome with another and fix DNA
breaks with remarkably few errors.
Draodurance is basically always on the
lookout for DNA damage and is set up to
be world class at DNA repair. But let's
explore what that means. Now, we could
either spend the next 30 minutes going
over the mechanics of Draodoans's vast
DNA repair arsenal, or we could quickly
cover the highlights and I can one day
produce a very laborintensive part two
video doing a much deeper dive. Hit me
up in the comments if you really want to
know the nitty-gritty about how Dinocus
Radio's DNA repair goes down. For now,
recombining DNA is radio's main weapon
here. Radiation and other things
primarily kill you by causing
doublestranded DNA breaks. that is
cutting through both helyses of your DNA
molecule. Dinocus radio has a robust
damage detection system and the star of
the show here is a protein called wre A
which forms these little fibers around
damaged DNA and then helps find a
matching sequence inside the duplicated
chromosome which other enzymes can then
use to synthesize a repaired DNA strand.
Now, the details here are a little hazy,
but REC A sometimes can team up with
another protein called DDRB and its
partner DDRA to help singlestrand DNA
breaks in a process called synthesis
dependent singlestrand annealing. And a
lot of scientists think this is the main
superpower draodurance has for
efficiently repairing DNA breaks.
Meanwhile, scientists studying
populations of draodurance that lived on
the exterior hall of the International
Space Station for a year found that
surviving bacteria upregulated these UVR
proteins. The UV radiation in the hard
vacuum of space forms all sorts of goofy
looking lesions on DNA like this. And
the UVR family of proteins does
something called nucleotide excision
repair to clean up the brakes. I really
could keep going. I mean, the map of DNA
repair and dinoccus radurans alone is
just wild and incredible, but I think
it's best to just put all these systems
in context. The upshot here is that
dinocus radioins can survive and repair
hundreds to thousands of doublestranded
DNA breaks while most other cells only
have the capacity to fix a few dozen.
And this robust DNA repair suite only
works because of all these DNA
redundancies our hero packages into its
nucleoid donut. Essentially, it is
really unlikely that the exact same DNA
break is going to happen across every
copy of D Radio's genome. Even if there
are multiple breaks across every copy,
radio will just recombine all the damage
and end up completely healed. This means
that draodurance not only can survive
radiation exposure, but actually thrive
under it, still growing and dividing
even when it's actively being irdiated.
A fatal dose of radiation for you barely
counts as background noise for this
fella based on the way that it's
optimized its living strategy. If you're
asking how this is possible, one review
paper I read chalked this up to an
investment strategy. Both the S layer
and this robust DNA repair system cost a
ton of energy. Most other bacteria
invest energy into growing and dividing
as quickly as possible while dinocus
radio is making more of an efficiency
play. Draodurance grows and divides much
slower than regular bacteria and they're
also a little bit larger too. But it
also has a much higher chance of
actually passing its genes on because it
can survive so much more. It's like a
quality over quantity play basically.
And that's all fun, but let's take this
to the next level because I've left a
few details out here. Here's the big
question. Do you know how radiation
causes DNA damage and therefore, you
know, damage to you specifically? I've
talked about this mechanism a little bit
in previous videos. In short, while the
high energy rays of ionizing radiation
can cook DNA on their own, direct damage
from ionizing radiation only accounts
for about 20% of the damage it does to
our DNA. The rest, 80%, is indirect.
Because ionizing radiation will bump
into just about anything, especially the
water that these cells are made out of.
Hit a water molecule in just the wrong
way and you can break it, creating truly
violent forms of oxygen called reactive
oxygen species or ROSS. These rapid
oxygen variants will flail wildly and do
huge amounts of damage to just about
anything they bump into. Which is why
Dinocus radio uses a deep antioxidant
pool. That's right. The antioxidants in
the D radioodderance S layer are there
to absorb the harmful ROSS byproducts
caused by radiation and other things.
I'll get to that later. Two of the worst
Ross characters are the super oxide ion
and hydrogen peroxide. Draodurance
employs a bunch of different super oxide
dismutase enzymes that disarm Ross
species before they can latch onto and
damage something else. This is why
antioxidants are such a big deal. Our
metabolism naturally produces a ton of
reactive oxygen species as a byproduct
of, you know, using oxygen to breathe.
The wild thing is radiation isn't the
only thing that kills you with reactive
oxygen species. Heavy metal poisoning
and other toxic chemicals can also cause
cytotoxicity by initiating a Ross
cascade. In a lot of ways, Dinocus radio
isn't trying to defend itself against
radiation. It's trying to defend itself
against reactive oxygen species. And
that's going to help us unlock the final
piece of the puzzle here. It's cool that
Radiodurans here can repair its DNA and
soak up a ton of ROS damage, but what's
stopping all these harsh conditions from
breaking the repair machinery, too? And
as an aside, this is one of the ways
that research exploring Dinocus radio
has unlocked our understanding of
radiation damage itself. Because it's
not the DNA damage itself that kills
cells when radiated, it more and more
looks like it's damage to cell
proteomes. Turns out radiation and
reactive oxygen species also cause a ton
of damage to the protein workers in
cells as well. Protein damage means that
the DNA repair system will break down,
which also means that busted enzymes
won't get replaced if they break, too.
So, we're stuck with a big question. How
does D-raodder shield its proteins from
getting damaged in the first place?
Antioxidant proteins can only do their
job if they're in the right shape. How
can this bacteria thrive under
consistent radiation exposure? And the
bacteria employs one more passive buffer
to tip the scales in its favor. And that
buffer is simple. It just maintains a
high concentration of manganese ions.
That's right, folks. Meet manganese. My
personal favorite metal on the periodic
table. Manganese ions power a lot of our
biology. In fact, some researchers
figure that the earliest life on our
planet ingested natural manganese
clusters as a kind of primitive
radiation defense. For me, most
importantly, manganesees forms the core
of the oxygen evolving complex in
photosystem 2, which is the molecular
ground floor our entire biosphere is
built on top of. And based on this poll,
manganesees basically gets no respect
for my audience. And this bit would be
far more effective if I personally
didn't misspell manganesees in the post
where I was trying to prove this point.
>> Manganese. So like even manganese's
biggest supporters don't give it enough
respect. Anyway, the oxidation state of
easy to find manganese ions makes them
great at absorbing the electrons on
things like the super oxide reactive
oxygen species. So, having a lot of
manganesees inside your cell and also
maintaining a high manganese to iron
ratio makes for an incredible first line
of defense against radiation damage that
helps guarantee that your critical DNA
damage repair enzymes don't get
kneecaped when oxidative stress arrives.
If you want to learn more about
manganesees, check out the episode MQ
Tate did on the element. Heck, check out
his entire ongoing periodic table
series. When it comes to analytic
chemistry, Mutate is the best and I will
accept no substitutes. But yeah,
Draodurance maintains up to hundreds of
times the manganese concentration you
would find in other cells. But
manganesees alone won't cut it. No one
is suggesting that you could just down a
manganese supplement and then walk into
the reactor at Chernobyl or whatever.
Instead, our hero also makes these short
little peptides that spontaneously form
passive antioxidant complexes by
accumulating manganese ions, phosphate,
and other metabolites into these
ephemeral little concentrations. During
times of radiation stress, these pockets
accumulate around Draodurance's DNA and
DNA repair proteins, forming an
incredibly powerful passive buff against
Ross damage. Meanwhile, Dradio takes
this manganese buff to the next level by
pumping manganese ions out of its
membrane and into the S layer and sugar
shield, supercharging this region's
ability to soak up radiation and
reactive oxygen species before that
stuff can even penetrate the cell. And
that kind of puts the whole thing
together. Dinocus radio can survive
extreme radiation doses thanks to the
interplay of a bunch of tiny factors
that add up to an incredible balance.
Dinocus radio is out here defending
every protein it can from damage so it
has the best chance to keep going. It's
not just one thing that makes Dinocus
radio so powerful. It's the interplay
between all these systems. Researchers
describe Dinocus radio as a remarkable
generalist. This bacteria just operates
in a way where it can take a bunch of
huge hits and keep going, which has
allowed it to survive basically anything
that life on this planet can throw at
it. But, you know, we have all those
details, but that that hasn't really
answered the questions I've set up here.
Why does Draodurance need to survive
thousands of times the radiation dose
that would instakill a person? I mean,
Earth has been radioactive in the past,
and the sun's a deadly laser and all,
but nothing has been this radioactive to
necessitate this much of a defense. What
are the actual evolutionary pressures
that would make something like this
evolve? And remember, radio durance here
isn't trying to survive radiation. It's
trying to survive the damage caused by
reactive oxygen species. Don't forget, a
lot of these proteins up in the S layer
are also helping our hero maintain its
shape. Radiation hurts, but it
definitely doesn't hurt like a hammer.
And the confusion here comes mostly from
how we framed our exploration of Dinocus
radiourons. We're thinking in terms of
radiation defense because that's a kind
of cellular damage that's relatively
easy to throw at model organisms. And
therefore, that was the question that a
lot of researchers were asking back in
the day. So, let's expand our focus a
little and try to complete this puzzle.
Here's one final piece that can help us
tie this all the way together. Another
protein class that's key to radio's
survival are these LEA fellas. When
things get hectic, these little LEA
proteins will condense into these long
helyses and help cells maintain their
shape. But what's the stress that LEA
proteins mitigate? Check this out. It's
desiccation. You know, drying all the
way out, mummification, whatever you
want to call it. And now we can start
really putting this together. Turns out
in the9s a team of researchers tested a
bunch of the radiation defense proteins
employed by dradio and found that those
factors also significantly protected
against desiccation which is incredible.
How does that even work? The theory here
is that as cells dry out these proteins
will condense into the long helical
chains you see here and prevent other
proteins from clumping together and
stabilize membranes once the internal
water pressure gives out. Once again,
maintaining structure is another really
important piece of draodurance's
survival puzzle. And this is enough for
me to start pulling together a more
plausible picture of what exactly
Draodurn developed all these systems
for. Here's the thing. Losing all your
water does a lot of crazy things, and
one of them is produce a ton of reactive
oxygen species and DNA damage, which
means we've been looking at this problem
all wrong. Radiation defense is just a
nifty side bonus of draodurance's
astounding ability to continue living
and thriving while the world around it
completely dries out. Which brings us to
a model for what exactly drove Dinocus
radio to evolve all these interconnected
systems. At its core, Dinocus radio is a
scavenger. It's going to lazily soak up
food from dead things and not cause too
much drama. Other organisms are going to
spend a ton of energy and compete for
food and resources, which makes things a
little more difficult for our hero. But
if the environment completely dries out,
then everyone else dies while
draodurance can use its repair systems
and interconnected antioxidant shields
to legitimately thrive, even when all
its rivals have effectively turned to
dust. When water returns, Radio Durans
will still have a relatively empty
playing field to thrive in before any
competition has time to get established.
And I love this view. I mean, sure, it's
cool that draodurance can entirely by
accident survive astounding levels of
ionizing radiation, but I love so much
that this bacteria developed this
incredible tapestry of interconnected
coping mechanisms simply because this
guy refused to die of thirst. And you
know what? I guess the way I framed the
title of this video might be a little
too clickbaity now. We've got an
entirely earth-based explanation for why
Dradio lives this way. I guess I'll just
have to sit back and take all the angry
comments now.
Except there are a few annoying details
that don't line up perfectly with
draodurance just surviving desiccation.
There's this overemphasis on UV
protection that goes beyond just the
damage you would get from drying out in
the sun. And why does radioodderans need
to make a cell wall out of like
radioactive cotton candy if we're
worried about the Ross generation inside
the cell? While research into this
bacteria is still ongoing and we're
still actively investigating potential
answers here, very late into the process
of making this video, I stumbled into
this review paper put out by the Cold
Spring Harbor Laboratory that briefly
laid out a theory that ties everything
together for me. Draodurance is
ubiquitous worldwide. And there are a
lot of ways that can happen, but here's
my favorite idea. Some bacteria form
spores and get swept up in air currents,
blown as high as the stratosphere, and
then are brought back to Earth by
rainstorms. Now while dinoccus radio
doesn't form spores it has shown that it
can thrive while desiccated which would
make it even easier for air currents to
carry it to altitudes where UV radiation
becomes more and more problematic. Up in
the stratosphere the bacteria would be
exposed to up to a thousand times more
potent levels of deadly UV radiation
from the sun. And since rain is the
primary vector for bringing airborne
cells back to Earth, the return journey
will very likely lead to a place where
there's more food sources for
draodurance to decompose. It all fits
together. So in the end, all this
defense might be a brilliant migration
strategy on the part of Dinocockus
radio. The easiest way to find new food
sources is to get taken there on air
currents. And this finally helps us
understand the S layer a lot better.
Because again, the main thing it
provides is a way to survive temperature
swings and structural support, which are
two things that become a huge problem
once you're fully desiccated and also
getting yeated into the upper
atmosphere. To summarize, docus radio
durans evolved to survive drying all the
way out and then getting blown to a new
food source. And that just had the side
bonus of also defending against the
mechanism that radiation damage uses to
destroy ourselves, which I think is just
incredible. While there's still so much
to learn about how and why Dinocockus
Radio lives the way it is, uh the
hilarious part of me making this video
is discovering that yes, it is entirely
plausible that Dinocockus radio durans
evolved effectively the equivalent of
space travel just to have a better
chance of finding new and interesting
patches of trash here on Earth. Now,
while even the highest parts of the
stratosphere aren't even halfway to the
technical definition of space, maybe you
could indulge me here real quick. Eh,
now there's just so much more to be
discovered about Dino Caucus radio, but
this is a decent enough introduction. I
am never not amazed by all the different
niches life can carve out for itself on
this good Earth. Our planet is
astonishing in the circumstances and
chemistry it can produce. And for me, it
is more than enough to account for all
the wondrous forms life can take. Even
though a lot of the research around
Dinocus radio tries to cast this as a
space bacteria or a Martian bacteria
that landed here, all of these proteins
and all of these systems are found
across our tree of life. And all of
Dinocockus radio's systems can be
explained by evolutionary pressures here
on this planet alone. Life on this earth
is astounding in its complexity. And
you're always going to find new and
interesting pockets where if you look
deep enough, you will be truly blown
away by the incredible ingenuity of
incremental change through evolution.
For me, this has just been a really fun
way to explore some really big subjects
here in this revolutionary moment in
molecular biology. But that's a good
place to end it, though. I really
appreciate your time. Thanks so much for
being here.
And hey, thanks so much for making it
all the way to the end of the video. If
you like this video, please make sure
you like and subscribe. I can't express
enough how much that helps. At the same
time, make sure you check out all the
cool stuff we have over at
patreon.com/clockworkshow.
That's the best way you can guarantee
that we're able to keep producing these
videos right now. Otherwise, head on
over to watchclockwork.com to sign up
for our free newsletter. Either way, the
very best way you can support this
project is being right here, right now.
Watching a video all the way through is
such an incredible help. Thank you so
much. For now, here's a weird one. Do
you have a favorite kind of mushroom? If
you do, let me know in the comments. I'm
trying to see something. I was overjoyed
when most everyone gave me the
objectively correct answer to the
question I asked in our last video, and
I want to see where this one takes us.
But either way, thanks so much for being
here. I genuinely appreciate your time.
As always, I'd like to leave you with
peace, love, and a high maganese to iron
ratio. Everyone, be well. Thank you so
much,
Maganese.