ED YONG: 1977.

A big year.

Saturday Night Fever.

Star Wars.

Apple becomes a company.

The first boomboxes take to the street.

Voyager 1 launches on an expedition

into the outer solar system.

And a small submersible named Alvin

begins a dive to the bottom of the Pacific Ocean.

[Splash]

[motor whirring]

February 1977.

250 miles north of the Galapagos islands.

A place where two continental plates

are pulling away from each other on the ocean floor.

Three men in a miniature sub set off

on an expedition that would completely

change our view of how extreme life on earth can be.

They were on the hunt for deep-sea hydrothermal vents

caused by the rift between those continental plates.

Their existence had been predicted for decades,

but no one had ever seen them.

At a depth of 7,500 feet their temperature sensors spiked

- they had reached volcanically super heated water gushing

through the ocean floor.

But they also found something that utterly surprised them:

life.

In extreme abundance.

Weird and wonderful.

How could this underworld support so much life?

There is zero sunlight here.

Skull crushing pressures and yet the Alvin crew

have discovered a hidden ecosystem.

This was NOT what they had expected.

They were the first to ever set human eyes

on this environment - rich and full of life,

like an underwater rain forest.

And then they found...

...the worms.

These bizarre creatures are tubeworms.

They are giants that can grow over six feet long.

Their bodies are encased in white tubes anchored

to the rocks.

At their upper end is a spectacular crimson plume.

It looks like a tube of lipstick that's been pushed out too far.

Or like maybe Mick Jagger's lips?

The Alvin team knew that they had

come upon a wonderful zoological oddity.

What they didn't know was that the worms would reveal

an undiscovered eco system, that we didn't even think

was possible.

The Alvin crew collects one of the worms

and gives it to this man.

This is Meredith Jones, the Smithsonian Institution's

curator of worms, and as befits his role as chief worm guy

he gives the thing a name: Riftia pachyptila.

Jones dissects the worm.

And he encounters something - that to us,

as non-worm people - is really weird: Riftia has no mouth,

no gut, no anus.

This thing has no way in, no way out.

How does it survive if it can't eat, digest, poop?

Well Jones, as a curator of worms,

had seen this kind of thing before - gutless worms.

Instead of a gut these worms have an organ

called a trophosome.

It's brown and spongy and makes up half the creature's length.

A trophosome isn't technically a gut,

but it does deal with nutrition.

But this trophosome was different

because there was nothing remotely like food in it.

Instead, it was packed with crystals of pure sulfur.

Something was going on inside this worm

that Jones had never seen before.

And that's when Colleen Cavanaugh enters the picture.

[Discotech music]

COLLEEN CAVANAUGH: I was a first year graduate student

at Harvard taking a course called Nature and Regulation

of Marine Ecosystems.

And the professors organized so that there

were four talks on the vents.

ED: Jones came in to give a talk about his worms.

It was a long talk.

Amazingly I was still awake when he

mentioned that in this trophosome tissue

it had sulfur crystals in it.

ED: What Jones knew that the water spewing

from the hydrothermal vents had a high concentration

of hydrogen sulfide, a potent toxin to most lifeforms.

So maybe the trophosome wasn't an organ to help feed the worm

- maybe it was a filter - something

to help get rid of all the poisonous hydrogen sulfide.

And when she heard that...

I immediately jumped up and said, "It- it's clear!

They must have symbiotic sulfur-oxidizing bacteria

inside of their tissues that are feeding the worm."

ED: Bacteria?

Bacteria!

CHORUS OF BACTERIA (SINGING): BACTERIAAA!!!

ED: And how did Jones react?

He was a little bit dismissive.

It was a little bit like, you know, sit down kid.

Ultimately I was able to get some tissue.

ED: Of the trophosome?

Of the trophosome.

So it looks like little pieces of brown tissue.

COLLEEN: It took a lot of detective work, chemical

analyses, DNA stains, scanning electron microscopy,

transmission electron microscopy.

ED: Ultimately?

I was right.

CHORUS OF BACTERIA (SINGING): BACTERIA!!!

ED: So Colleen discovered that trillions of bacteria are

living in the trophosome, using the hydrogen sulfide from

the vents as an energy source...

...in a process called chemosynthesis.

COLLEEN: Chemosynthesis is a process

using chemicals such as hydrogen sulfide as energy sources.

ED: As opposed to photosynthesis which uses sunlight.

Plants do photosynthesis.

They need wat-eh-hem, um.

They need water and carbon dioxide,

which they transform into sugars using the energy in...

sunlight.

But the worms can't do that.

COLLEEN: It's dark.

We're two and a half kilometers down up to,

I mean to even deeper.

That's, you know, over a mile and a half deep.

So it's complete darkness in the deep sea.

ED: So instead of sunlight the bacteria ingest and process

the sulfides from the vents.

[sucking/slurping sound] In doing so they excrete sulfur,

but they also release energy which

they use to make food for themselves and for the worms.

[Bacteria eating, burping, and farting.]

And that's what chemosynthesis is.

Making food not with solar power, but with chemical power.

So it's apparent from a mouthless and gutless

point of view that the worm is benefiting from getting

it's food from the bacteria.

When you're a bacterium inside of the animal

and you've somehow convinced the host

to provide you with the sulfide and the oxygen

then you're, you have easy street.

ED: So it's good for everyone?

That's right

Ok so one things not quite tracking with me here.

So, if Riftia has no mouth how do

the bacteria get into it in the first place?

So we found out that the bacteria were actually

getting in through the skin, through the body

wall into the, the worm.

Wow!

Ok so how do the sulfides get in?

So the hydrogen sulfide goes in via the plume.

(Pause) So they do have a mouth?

It's more, it's more like a lung.

But a lung is for breathing...

Thats right.

It's breathing oxygen just like you and I.

But it's also effectively breathing

hydrogen sulfide because that's what

the bacteria need to produce organic compounds

via chemosynthesis.

And that deep red of the plume I mean

it almost looks like blood.

COLLEEN: It is blood.

They have a blood supply all the way through it.

And the blood is carrying the hydrogen sulfide,

the oxygen into the trophosome to the bacteria.

ED: Huh.

And this type of chemosynthesis is it just a worm thing?

Not at all.

It's ubiquitous, or it's, it's widespread in nature.

Wherever sulfide and oxygen exist we can look for it

and it's found in many of those places.

ED: Chemosynthesis had been discovered a hundred years ago,

but after Colleen's discovery, it

was established as the basis of this entire new ecosystem,

7,500 feet below the surface.

And in fact, chemosynthesis might

have been the way the earliest lifeforms on the planet

found a way to survive.

COLLEEN: It took kind of getting away from sunlit environments

to see that it's really possible and that the whole ecosystem is

dependent on the chemicals - in this hot water that's

coming up.

It's like the fountain of life.

ED: Very cool, these vent creatures.

COLLEEN: It's actually very warm.

Well they're in hot vents.

[Laughs] Sorry.

And I think we'll leave it at that.

If you're especially curious about the story

behind this episode, check out the link

below for an article that dives even deeper

into these amazing microbes.

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Thanks for watching.