[music] 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 eachother on the ocean floor.

Three men in a miniature sub set off on an expedition that would completely change our view of howextreme life on earth can be.

They were on the hunt fordeep-sea hydrothermal vents caused by the rift betweenthose continental plates.

Their existence had been predicted for decades, but no one had ever seen them.

At a depth of 7,500 feet theirtemperature sensors spiked - they had reached volcanicallysuper heated water gushing through the ocean floor.

But they also found somethingthat 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 aspectacular crimson plume.

It looks like a tube of lipstickthat'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 wasthat 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, theSmithsonian Institution's curator of worms, and as befitshis 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 reallyweird: 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 makesup 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 nothingremotely 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 ColleenCavanaugh enters the picture.

[discotech music] COLLEEN CAVANAUGH: I was afirst year graduate student at Harvard taking a coursecalled 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'tan organ to help feed the worm - maybe it was a filter - something to help get rid of all thepoisonous hydrogen sulfide.

And when she heard that...

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

They must have symbioticsulfur-oxidizing bacteria inside of their tissuesthat 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 discoveredthat 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 hydrogensulfide 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 intosugars 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 completedarkness in the deep sea.

ED: So instead of sunlight thebacteria ingest and process the sulfides from the vents.

[sucking/slurping sound] Indoing so they excrete sulfur, but they also release energy which they use to make food forthemselves and for the worms.

[Bacteria eating, burping, and farting.]

And that's what chemosynthesis is.

Making food not with solarpower, but with chemical power.

So it's apparent from a mouthless and gutless point of view that the wormis 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 toproduce 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 thetrophosome 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 beendiscovered a hundred years ago, but after Colleen's discovery, it was established as the basisof 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 gettingaway from sunlit environments to see that it's really possibleand 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.