Original subtitles

Bacteria.

They're everywhere.

They're invisible to the human eye

and they're incredibly prolific.

In just one millimeter of fresh water,

there are a million of them.

In a single gram of soil, over 40 million.

Together, they weigh more

than all the plants and animals in the world.

Humans may think they rule the world

but in reality, they're just lodgers on a planet

whose first inhabitants were bacteria.

All living beings are covered with them,

on the inside as well as the outside.

In a human body, there are 100 trillion of them.

We're actually more bacterial than human

by about 10 to 100 fold.

We truly are less human than we think.

Bacteria are generally very misunderstood.

People think bacteria mean illness,

but that's not true at all.

In fact very few bacteria are dangerous to humans.

The fact is,

the relationship that plants and animals have to bacteria

is often beneficial to both.

These beneficial relationships are called symbioses.

I can't think of a single animal

that's not symbiotic, especially us.

We couldn't live without our bacteria.

Symbiosis has played a fundamental role

in the evolution of life.

We found out during the course of the 20th century

that associations between symbiotic species

were more common than we thought

and are definitely one of the greatest motors of evolution.

Deep down at the bottom of the ocean

lies the mysterious world of the abyss.

Here in the greatest desert in the world,

there's no plant life and very few animals.

But when in the 1970s,

oceanographers discovered the first deep see vents,

the phenomenal amount of animal life they found there

in an environment hitherto thought hostile to all life forms

raised a lot of questions.

Could bacteria really survive in such extreme conditions?

Were they responsible for this profusion of life?

Could symbiosis explain

these creatures' extraordinary success?

To find answers to these questions,

the BIOBAZ oceanographic expedition,

founded and led by professor François Lallier

of the Roscoff Biological Station in Brittany,

took us in search of secrets hidden since the dawn of time,

many fathoms beneath the sea.

We're on course for some volcanic sites

out in the middle of the Atlantic.

There are 32 scientists on board

and they're all experts on deep sea vents biology.

The state of the art technology

of their remote controlled robot, Victor 6000,

will enable them to minutely explore the volcanoes

of the mid-Atlantic ridge.

Victor can dive to depths of six kilometers.

It's setting off into a world of total darkness,

heading for one of the most spectacular

deep sea vents on the planet:

Rainbow, which lies at a depth of 2,300 meters.

It's hard to get close to Rainbow.

Powerful geysers constantly pump out

gigantic swirls of scalding liquids into the abyss.

It's a boiling stew of highly acidic fluids,

their chemical composition a long list of toxins,

each more dangerous than the other.

Yet, here at these geysers,

there swarms an impressive quantity of animal life.

And right here among all the chimney systems

created by the geysers,

hides the first creature the scientists want to study,

the Rimicaris shrimp.

These chimneys, covered in cracks,

are the only ones that release their fluids

gently and regularly enough

to provide the shrimps with ideal living conditions.

The Rimicaris huddle into the channels of volcanic fluids,

dancing together in an eternal ballet,

as if in defiance of the most extreme conditions

to be found anywhere on the planet.

Aboard the boat, under the leadership

of Marie-Anne Cambon and Magali Zbinden,

everyone's getting ready for the catch.

They're hoping for a haul of 100 Rimicaris shrimps.

It's easy to catch them.

You just Hoover them up.

Coming up to the surface,

the animals will suffer the traumatizing effects

of violent decompression.

Down here at 2,300 meters,

the pressure is 230 bars,

that's 230 kilos per square centimeter.

At the surface, the atmospheric pressure

is just one kilo per square centimeter.

We ourselves are organisms that contain gas.

If we are compressed at 300 bars,

our thoracic cage is immediately squashed,

which of course means instant death.

Fortunately, these deep sea organisms

contain no gases.

It's more a question

of the fluidity of cellular membranes.

We know that if we vary pressure, then fluidity varies, too.

And membranes hold all an organism's

channels of transmission:

neural transmission, chemical transmission, etcetera.

From the moment you disturb

any of an organism's membrane passages,

if the variations in pressure are too much,

the organism will die.

At sea level pressure,

the Rimicaris shrimps of the Rainbow vent

cannot survive longer than a few days.

But their anatomy still remains intact enough to be studied.

Dissection of their digestion tube

reveals the first enigma

of these creatures' strange way of life.

Apart from a few morsels of rock

that they've nibbled here and there,

their intestines contain no food at all.

The shrimps' digestive system

doesn't appear to play a major role in their feeding habits.

So, what then do they live on?

The researchers naturally turn their attention

to the strange crustaceans' enormous head.

The head takes up half the creature's body.

That's very big.

Normally, it's not even a third.

When they're very young, they look like ordinary shrimps

and at a certain point in their development,

they metamorphose,

a bit like a caterpillar turning into a butterfly.

The head become so enormous, and the shell too,

that the shrimp can't graze anymore and can't feed.

No wonder the digestive tube's almost empty.

As for the huge head, that's due to the terrific size

of the chamber that hold the gills,

the animal's respiratory organ.

When they take a look inside that chamber,

the biologists get a big surprise.

There are billions of bacteria living there.

The bacteria have to get into the gill cavity,

so that creates really long filaments.

And they also get into the scaphognathite,

which is a kind of blade

that pulsates in the cephalothoracic cavity

to create a current of water,

and has long bristles on it that are covered in bacteria.

Microbiological analysis

shows that these resident bacteria

are always the same species.

In the absence of a true functioning digestive system,

the researchers wonder if, when it comes to food,

there isn't a relationship between the shrimps

and their vast colonies of bacteria.

A kind of symbiosis, even.

But to find out more about this strange relationship,

you have to work with healthy shrimp specimens

that haven't been through the shock of decompression.

And that's what Bruce Shillito's team intend to do

on a second trip to the Rainbow site,

with the help of a revolutionary new

high pressure aquarium system.

To thrive with such success in such different environments,

bacteria must have an amazing ability to adapt.

The next step of the mission

will be to verify this hypothesis at another site.

So the course is set for Lucky Strike,

another volcano discovered in 1992

down at a depth of 1,700 meters.

The deep sea geysers at Lucky Strike

aren't as powerful as the ones at Rainbow,

so they haven't developed those spectacular

tall black and gray chimneys.

Over the decades, they have simply built up

a succession of little hills.

The whitish carpets that surround the Lucky Strike geysers

are actually vast colonies of bacteria

visible to the naked eye.

The first thing you notice

are they big layers of microbes,

like big yellowish-white carpets

that cover the sediments of the seabed

and the ends of the chimneys.

And the extraordinary thing

is that they're actually long filaments

that float in the current.

These carpets of bacteria are flirting dangerously

with the scalding emissions of fluid.

Probes, placed by the team right inside the chimneys,

show temperatures of over 350 degrees.

But as they mix with the sea water

that's at only three or four degrees,

within the space of less than a meter,

the temperature of the fluids drops to less than 30 degrees,

thus creating conditions that favor the development

of most species of bacteria.

The chemical composition of the fluids, though,

presents all the characteristics of an environment

hostile to most life forms.

They are highly acidic and contain

radioactive elements, heavy metals,

and highly toxic molecules such as sulfurs.

From our point of view, of course,

what with the pressure, the temperature, and the chemicals,

because there are plenty of compounds there

that would be toxic to animal life,

the conditions look extreme.

For these bacteria, it's simply their habitat

and they're fine there.

Researchers have discovered

that the bacteria feast on the volcanic fluids

as if they were nectar.

All those toxic elements, deadly poisons for us,

are for them a source of nourishment.

Obviously, we find our human enviroment

a more welcoming place than a volcanic abyss.

But these bacteria have no need of a human body.

They're quite at home here.

Not many scientists know more about

the role bacteria play in our lives than Lora Hooper.

In some ways we can consider the intestine,

and maybe even the skin, an extreme environment,

in that these bacteria have to cope with an immune system,

for example, that's lobbying grenades at them all the time.

They have to cope with shifts in pH

as they travel through the stomach and to the intestine,

and vast changes in diet.

Bacteria's ability to survive is remarkable.

For billions of years, they were the only living creatures

to colonize the deep sea geysers.

But across millions of years of evolution,

some enterprising creatures from the surface

have adapted to the conditions here

and even managed to settle in permanently.

So who are they, these pioneers,

and how do they withstand the extreme conditions?

Jozée Sarrazin leads an animal ecology team

that specializes in deep sea geysers.

To gauge the capacity of animals

to colonize new ground around the geysers,

she has come with a system of artificial habitats,

made up of slate, wood, muslin, and even beef bones.

The whole range of them is laid out close to the fluids

and recuperated sometimes a few days later,

but more often the following year

during the next expedition.

In the space of just a few days,

bacteria from the surrounding water have managed

to settle on all the different habitats.

In their turn, they have soon attracted

dozens of local species of a particular kind of animal,

the grazers.

The first animals

fed directly on the bacteria, just like cows at pasture.

They came to graze the fields of bacteria.

Millions of years ago,

thanks to the bacteria that formed the basis of their diet,

the very first animal species from the surface

were able to survive in the vicinity

of the deep sea geysers.

There are little gastropods, little sea snails.

There are also little amphipods, little crustaceans

that graze on the bacteria.

Colonization of the geysers of the abyss

could have ended there with the grazers,

content just to eat the bacteria they found

without establishing any further relationship to them.

But the grazers have had nothing like

the success of other species

that have gone on to develop gigantic colonies.

Species like the so called Azorean deep mussels,

which are particularly numerous at Lucky Strike.

One of the aims of the BIOBAZ program

is to find out the reasons for this exceptional success.

The next dives of the robot Victor

will be entirely dedicated to the in depth study

of the deep mussels' way of life.

Whereas Rimicaris shrimp are only to be found

at depths of more than 2,000 meters,

deep mussels are present wherever there are hot geysers.

The Lucky Strike deep mussels

are harvested at depths of less than 2,000 meters

and stand up well to the decompression.

The scientists can simply transport them in Plexiglas boxes.

What's most striking

when you open a deep mussel, is the sheer size of its gills.

In this mussel, we found bacteria in the gills

and in great abundance, too.

There are no bacterial filaments

visible on the outside, though.

Unlike with the Rimicaris shrimp,

the deep mussel bacteria live right inside

the cells of the gills, a very rare phenomenon.

The cells on the surface

of the thousands of little filaments that make up each gill

have the specific task of growing internal bacteria.

It's quite clear when seen through a fluorescent microscope,

the nucleus of the cell is blue.

The hundreds of little red and green blobs are all bacteria,

comfortably lodged right inside each specialized cell.

So the bacteria pull off the amazing feat

of fooling the cells' immune systems to get inside them,

and once in, to stay there.

The animal has to be able to regulate

the rate of growth of the bacteria within its own cells.

In certain types of cells, the bacteria are allowed,

even encouraged to develop,

whereas in all the other tissues,

there are no symbiotic bacteria to be found at all.

But the mussels don't merely accept

the presence of the bacteria,

they make sure that their guests can eat their fill.

Mussels are in fact like filters.

They circulate water through their gills.

There's oxygen in this water as well as sulfurs,

a bit of methane, and a bit of dissolved carbon.

So everything the bacteria need is there,

and since the water's circulating,

their environment is constantly being refreshed.

This relationship between the bacteria

and the mussels is most peculiar.

It's as if, after millions of years

of an intimate relationship,

the bacteria were progressively becoming part

of the very cells of the mussel.

To measure to what extent the deep mussels

are dependent on the bacteria in the cells of their gills,

the scientists at BIOBAZ

are going to try a little experiment

1,700 meters under the sea.

It consists of putting a few dozen mussels in cages

at a distance from the source of the fluids.

When we take them out of their natural habitat

the bacteria get no more sulfurs, no more methane,

so they have nothing to live on.

Away from the fluids,

the bacteria cease to multiply and eventually disappear.

And without their crop of bacteria,

the mussels only survive for two or three days.

What is the reason for this fundamental dependence?

The gills are like their larder,

where they grow their bacteria.

Astonishing as it may seem,

each of these specialized cells

is constantly digesting within itself

a small part of its personal stock of bacteria.

We also think the bacteria

are capable of releasing compounds.

For example, as a bacteria grows up,

it will release sugars around it

within the cell of the animal.

By way of the blood circulation,

molecules from the intracellular bacteria in the gills

actually feed all the mussels' cells.

So it's an especially close symbiosis

between animal and bacteria

and it's the reason these deep mussels have done so well

in such extreme conditions.

An intracellular symbiosis like this

is a very rare phenomenon in biology.

It's an extremely important discovery,

since it demonstrates the fundamental role

that bacteria have played

in the most important phases of evolution.

As long as two billion years ago,

the symbiotic fusion of two bacteria,

in a process resembling that of intracellular symbiosis,

was possibly at the origin of the first cell with a nucleus.

Soon after that, the incorporation of a bacteria

enabled cells with nuclei to breathe oxygen

and evolve ever more complex organisms

all the way up to mammals and to the human species.

A few hundred million years later,

it was once again symbiosis with a bacteria

that would allow cells to photosynthesize

and enable algae and all the earth's vegetation to evolve.

So two of the most easily recognizable

characteristics of plants and animals

come from bacteria that they breathe,

or in the case of plants, photosynthesize.

These both originate from symbiosis with bacteria.

These huge populations of symbiotic mussels

became an important food source for other animals

coming from the surface.

This third type of animal

was neither a grazer nor a symbiotic.

They were predators, scavengers, and bottom feeders.

They may be the spitting image

of their cousins at the surface,

but these carnivores have adapted so well

to the extreme physical and chemical conditions here,

that they have become species

specific to the deep sea geysers.

Take the Mirocaris shrimp, for instance,

a distant cousin of the Rimicaris with its huge head,

or the Segonzacia crab,

both of them scavengers and bottom feeders.

These native species spend their whole lives

around the sources of volcanic fluids

and are perfectly happy here.

But at another nearby site 800 meters deep,

there's another large species of crab, the Chaceon.

This big crustacean doesn't live here at the geysers,

it just drops by from time to time,

drawn by all those mussels.

Unlike the local crabs,

the Chaceons can't withstand the fluid emissions

and often come away with painful burns.

But their daring is rewarded with copious meals.

Those huge banquets have their downside, though.

All the creatures of the deep sea geysers

have had to get used to the presence everywhere,

in the water and in their food, of a lot of toxins.

Top of the list, hydrogen sulfide.

There's always plenty of that in the fluids.

It's what make rotten eggs smell so bad.

It's a molecule, that in contact with the air,

gives off a very nasty smell.

It's a molecule, that for an animal, for example,

is highly toxic

because it replaces the oxygen in the hemoglobin,

so if you breathe in sulfur, it can asphyxiate you.

So the local inhabitants

have adapted to the need to detoxify these chemical elements

but what is the strange hair

that most of the crabs seem to be covered with?

Well, guess what?

It's bacteria.

Generally, if a bacteria

can lodge itself on an animal,

that means it's been accepted and will benefit the animal.

When the bacteria draw in heavy metals

or elements like sulfurs,

they transform them in order to grow,

and so what they put back into the environment

is less toxic than what they took in.

That's what we refer to as detoxification.

The bacteria grow on the crabs

because they like it there.

It's like having their own chauffeur-driven ride.

One that keeps them neither too near, nor too far,

from those nourishing fluid streams.

It is indeed a kind of external bacterial symbiosis.

We ourselves also wear an overcoat of bacteria,

but ours is totally invisible.

Our bodies contain 10 times more bacteria than cells.

The mucous membranes of our respiratory system and genitals,

as well as the insides of our digestive tube, are carpeted,

and the surface of our body covered with them.

It's known that there are approximately a million bacteria

per square centimeter of skin,

and interestingly, if you wash your hands,

that will go down, but only very temporarily.

So 30 minutes later, they're all back.

They are making their home there

so that other pathogenic bacteria

are less likely to be able to successfully colonize,

but they also stimulate the immune system of the skin

and so that confers some protection as well.

Our best friends are the bacteria on our skin.

In exchange, we feed them with the dead cells

that are the product

of the constant renewal of our epidermis.

Just as with the crabs down in the abyss,

it's a question of symbiosis, of mutual aid.

Let's return to the Rainbow cleft,

where the Rimicaris shrimp has carved out its little domain.

To further their research on the relationship

between the shrimps and the bacteria they carry

in their outsized heads,

the team needs to be able to observe some healthy specimens

that haven't suffered the effects

of such brutal decompression.

Bruce Shillito's team has come up with

a little technological jewel, made up of two parts:

PERISCOP and BALIST

that can bring shrimps up to the surface

while maintaining the pressure from down below.

It's a totally unique invention.

It's the only machine that can connect with a cell

that can itself harvest quite sizable animals.

Of course, we're not talking about giant squid,

but five centimeter shrimps is still pretty good.

With food preservation, we talk about the cold chain,

but here we're talking about the pressure chain.

From the place they were caught

right up to where they're studied,

we maintain the pressure of the seabed

and maintain the most natural conditions possible.

BALIST, the more complex part of the system,

stays on board the boat.

It's impressive stainless steel structure

weighs nearly 400 kilos

and means it can recreate the extreme pressure conditions

of the abyss.

It works like an airlock,

a bit like on a space shuttle.

Like a craft that comes and connects

to the space station to supply it.

We pressurize the water lock, the connection,

then once everything's at the same pressure,

we open the main valves just a quarter of a turn

and we can transfer the animals just by tipping it all in.

The first into action, though,

is PERISCOP, the movable part.

It is placed on the elevator,

a freestanding module that shuttles up and down

from the surface during Victor's dives,

which can last up to 36 hours.

The mission of the robot's pilots

is to catch 20 Rimicaris shrimps inside a sealed tube

they call the "PERISCOPette."

First stage accomplished.

Victor straight away takes control of PERISCOP,

which is a few hundred meters away on the elevator.

Fitting the PERISCOPette full of shrimps

into PERISCOP's steel cylinder

is the most delicate maneuver of the whole operation.

Now it's just a case of closing the powerful valve

that will maintain the deep sea pressure

all the way to the surface.

After a few minutes, the elevator casts off its ballast

and its buoyancy carries it back up to the surface.

Back on board,

Bruce Shillito is preparing a cozy nest for his guests.

Inside BALIST, the shrimps will be quite at home.

The water is at eight degrees

and the pressure is around 230 kilos per square centimeter.

Through the window of three centimeter thick sapphire,

the scientists can observe the animals

throughout the experiments.

That's it.

Watch the handle.

The last phase of the operation

is to connect PERISCOP to BALIST

without any loss of pressure.

One, two, three.

Is that good for you guys?

On the trolley, there.

Put it down gently.

That's it.

Okay.

Put it where it usually goes so it'll be clear.

It's not quite in the joint yet.

Almost, almost.

A bit further onto the plate, keep sliding.

More, more.

Slide it.

A bit more, okay that's good.

Now we unscrew it.

That's it.

Before he opens the powerful water lock,

Bruce has to balance to the nearest gram

the pressure in both BALIST and PERISCOP.

Now I balance it with BALIST

so the water lock's okay.

Now for this.

Okay.

Only now can they transfer the Rimicaris.

But despite the sloping angle of the system,

the PERISCOPette refuses to go down.

It looks like one of the valves isn't perfectly aligned.

I think I hit it.

It felt like it was going in there.

It's going through, it's fine.

You got something going on your end?

Right, wait. I'll close it.

We messed it up once with Girard

and all three of us were banging on the tube there.

Okay, wait.

The shrimps can survive inside BALIST

for up to four days.

In the aquarium, we can control the temperature,

we can control the flow and pressure,

and that allows us to carry out

a lot of interesting experiments.

The various experiments carried out

using the PERISCOP BALIST system

will lead to a surprising discovery.

We'd always thought that the shrimps

grazed on the inside of their gill cavity,

that it was like a growing chamber

and that they scratched at the bacteria there to eat them.

But then we found out that the covering of bacteria

was never actually scratched or damaged.

Unlike the deep mussel,

the shrimp does not eat the bacteria in its gill cavity.

On the contrary.

The research shows that the bacteria actually

feed their host just by transferring molecules.

The bacteria produce organic molecules

that are defused by passing though the skin of the animal.

This must mean that the internal surface

of the gill chamber lets food molecules through

directly into the creature's blood supply.

This is amazing news.

Could it mean that there's a direct comparison

between the huge head of the shrimp

and our own large intestine,

which also contains billions of bacteria?

Human intestinal bacteria help us to digest.

We have our gastric juices of course,

but they can't digest everything we eat.

We think it's more or less the same thing for the Rimicaris.

Basically it's a shrimp that has its intestines in its head.

However the exchange

between the Rimicaris shrimp and its bacteria,

goes a lot further than that between

our intestines and theirs.

A human being has to ingest a certain amount

of vegetable or animal sustenance every day,

which helps to build up the body's cell structure.

The main purpose of our intestinal bacteria

is to help us digest our food.

They're producing metabolites that we can utilize,

they're also breaking down dietary substances

like complex polysaccharides

that we don't have the enzymes to digest.

So they're very beneficial to our digestion in that way.

But it's quite different for the Rimicaris shrimps.

They don't even need to eat.

The molecules they need to survive

are entirely provided by their bacteria.

It's magic, really.

Very well organized, anyway.

For true symbiosis to occur,

the relationship has to be beneficial to both parties.

So what's the advantage here for the bacteria?

The shrimp provides the bacteria

with a closed cavity

where nothing else can get at them to eat them.

Well, the shrimp provides them

with a home, of course,

but it also invites them to dinner.

It provides constant access to the sulfurs

and other energy sources present in the volcanic streams.

The shrimps going back and forth into the heat

but not for too long.

Like, "Oh, ouch! That's enough, better cool off a bit."

But the bacteria get their hydrothermal fluids

that enable them to multiply and prosper

and to provide the shrimp with its organic matter.

It's a risky business, though.

Sometimes you come across shrimps

whose shells are burnt and have bits of them damaged

and this is certainly because

they got too close to the fluids

and have been burnt by them.

Our intestines, too, offer food and board

to a vast community of bacteria.

They enjoy a safe environment and,

except in very hard times, all the food they can eat.

It turns out that it's actually

a mutually beneficial relationship.

Scientists have made enormous progess

in understanding these remarkable symbioses,

but there's still a lot left to learn.

How and when, for example,

do the baby deep mussels or Rimicaris shrimps

first acquire their bacteria?

The researchers have just found

the first seed of an answer to this

with the Rimicaris shrimps.

This is definitely a very mysterious creature

and we don't know its life cycle.

They carry a few eggs under their abdomen

until they have a young larva that can swim,

and we find bacteria on the outside of the eggs.

It would appear that the bacteria

are already there on their eggs.

The human fetus, by contrast,

protected in its mother's uterus,

is completely sterile.

The mother's immune system

represents an impenetrable barrier to any bacteria.

So for us, the whole question of bacteria

only starts at the moment of our birth.

Early in life, the bacteria that occupied the neonate

are generally from the mother's microbial flora.

But the developing child, in the case of humans,

quickly acquires its own microbiota

and this develops into an adult microbiota

during the first years of life.

Man is just one piece

of earth's great biological puzzle,

where it's the bacteria who reign supreme.

That's the beauty of bacteria.

They can adapt to anything.

To them, from their perspective,

probably nothing is an extreme environment.

Bacteria may have been the very first

living beings on earth,

but they've never tried to wipe out more complex life forms.

On the contrary, they've constantly helped,

stimulated, and accompanied the evolution of live.

The remarkable success of the bacterial symbioses

found down in the abyss

has shed a lot of light on the fundamental importance

of mutual aid between creatures

when it comes to maintaining life on earth,

including our own.

Here down in the deep, acidic, burning geysers of the abyss,

it's as if hell itself opened its jaws to show us

how symbiosis is the key to the future of all life on earth.