[music playing] ED YONG: Orson Welles said we're born alone, we live alone, we die alone.

Orson, you are mistaken.

Even when we think we're alone, we aren't.

We are completely surrounded by microbes.

They live on us.

They live in us.

They are everywhere.

Every one of us is amulti-species collective, and with these microbes, we exist in symbiosis, a wonderful term that refers to differentorganisms living together.

Animals and their microbes go through life in this long waltz, andsome of these partnerships take hold at the moment of birth.

Animals have many waysof passing their microbes on to their offspring.

Here is a beewolf, an aptlynamed wasp, a fierce predator on the hunt for honey bees.

[buzzing] This one is a female and she'slooking for food for her young.

[buzzing] The beewolf stings the bee, but she doesn't kill it, she just paralyzes it.

A dead bee would rot, but thisway, it stays nice and fresh.

[music playing] The beewolf drags the bee down into her burrow and lays an egg on it.

And when the egg hatches, the grub starts to eat the bee alive.

Once it finishes, the grub and encases itself in a silken cocoon and starts transforming into an adult.

[music playing] So the beewolf mother hasgiven the gift of a honey bee to her young, but it's not the only gift.

Meet Martin Kaltenpoth.

He studies beewolves.

Hey, Ed, how is it going?

Hi Martin.

So let's get right to the paste.

Because when you were doing your PhD, your advisor noticed something weird about beewolves that they secrete thispaste from their antennae, like toothpaste coming out of a tube.

Yes, and that's reallyweird because no other insect is known to secrete such large amounts of stuff from the antennae.

So why do the beewolves do this?

This kind of an exit sign for the larvae to leave their cocoon and get out of the ground.

ED: But there's more to the story, right?

Because when you looked atthe paste under a microscope, you saw something weird.

MARTIN: I still remember sitting there with my PhD advisor in his office, we looked at the pictures,we're like, wow, this is weird.

This is full of cell-like structures.

So there's some bacteria and that was fascinating because it was completely unheard of in an insect antennae.

ED: So there were bacterialiving inside the beewolf antennae, which is astrange place to call home, even for a microbe.

What was it doing in there?

No matter what it took, Martin was going to answer that question.

He became obsessed by bacteriawhich I could understand.

He examined beewolves from around the world and in every one, he found bacteria teeming in their antennae.

And even more surprisingly, those antennae only contained one type of bacteria-- streptomyces.

MARTIN: It was amazing tosee, wow, it's streptomyces, and then even to us, as zoologists at that time, it did ring a bell.

[buzz] Because streptomyces is so wellknown for antibiotic production and we use it, as humans, we useit for human medicine, as well.

ED: And that was a big discovery.

Streptomyces is a vast groupof bacteria, many of which are the source ofantibiotics, the drugs that we use to kill other microbes.

So the question became, were the streptomyces making antibiotics thatsomehow benefited the beewolf?

[buzzing] Martin spends a lot of timewatching beewolves, watching their cocoons, their grubs, looking at their symbiotic bacteria under a microscope.

And eventually, Martin found something.

The fibers of the cocoon weresaturated with the paste.

The grub is covered in a protective blanket of streptomyces and it needs all the help it can get.

For nine long months, it's trapped in this warm, humid chamber that's perfect for nurturing fungiand bacteria, the kind that cause disease.

MARTIN: In the cocoon, it's pretty dark, so the larva is sitting there or lying there in the dark for about nine months, and very lonely.

So there's nobody to protect it, to help it.

Ooh, except for the antibiotic producing the bacteria.

Exactly, yeah.

But that was just a hypothesis, right?

So you didn't know if theantibiotic paste actually protected the young beewolf.

Not really, so the next step was testing whether the microbes indeed have a benefit for the beewolves.

[music playing] So Martin dividedbeewolves into two groups.

One, he raised normallywith access to their paste, and the second, he deprivedthe paste and then he waited.

MARTIN: Yeah, I mean, I would check them daily and see how the larvae with andwithout bacteria were doing.

I would never know whether theymight still survive and emerge successfully.

So would the beewolves survivewithout their antibiotic paste?

Well, almost all of the youngbeewolves that he deprived of paste died from infections.

While those that had access to the paste, they usually survived.

The results were crystal clear.

By analyzing the chemistry ofthe bacteria in the cocoons, Martin's lab confirmed that they were indeed, producing a cocktail of antibiotics and the young beewolvesexploited those chemicals to protect themselves from other microbes that might cause disease.

But this is a two way relationship.

Those defensive bacteria might benefit, too.

MARTIN: The antenna is like a nice and secure place for the bacteria, becausethey get all the nutrition from the beewolf, so that'swonderful, a wonderful place to be.

I mean, I don't know whether they're happy in there, they look happy, butthat's a difficult question to ask a bacterium.

But how did those bacteria get into the antennae in the first place?

Well, take a look at whathappens when the young beewolf emerges from its cocoon.

Right before the beewolffemale leaves its cocoon, it will rub its antennaeagainst the cocoon surface and take up its bacteriabecause it will need them later to give it to its young.

ED: It's a bacterial inheritance to go along with the genetic inheritance.

Kind of like us, we're notso different from beewolves.

Humans also get our firstmicrobes from our mothers, but we spend nine months not in a cocoon, but in a womb, a chamber that separates babies from the outside world.

And at birth, we unitewith the world's microbes.

Think of how significant that moment is.

In just our first few seconds, we transform from just an individual into an entire world, acolony, a thriving ecosystem.

And with every newexperience, that ecosystem changes in ways that scientistsare still trying to figure out.

We pick up more microbes fromour parents' skin, our mother's milk, the blankets we are swaddled in.

We change and transform throughout our lives and when the time is right, we pass on our microbes to our own children.

None of us dances alone.

We all contain multitudes.