The Magic of Mushrooms

Of all life on Earth, there's something more mysterious

yet more vital to our survival than anything else.

Its birth is violent.

Much of its life is hidden underground.

And only at the end of its life cycle does it reveal its identity.

The mushroom.

I'm Professor Richard Fortey.

'I've been fascinated by mushrooms all my life.'

Nice find.

'I love to collect and study them.'

Many people think of mushrooms just as something to eat,

or maybe as decoration in folk tales.

But nothing could be further from the truth.

They have a secret life so magical,

so weird,

that it defies imagination,

and I'm going to reveal it as never before.

I've set up my own lab to unlock the mysteries of mushrooms.

Oh, look at that!

They're like geysers.

I'll discover their astonishing powers.

What makes them the fastest...

the largest...

..and some of the deadliest living things on the planet.

Half a cap will kill you and kill you slowly and painfully.

And I'll meet the people turning those powers to our advantage

to create new medicines

and new materials.

The innovation we have here is the future of energy production

and even devices and products like your iPhone.

To discover what gives mushrooms their extraordinary abilities,

I'm going to follow their story from birth, through life, to death.

A story so strange it seems almost alien,

yet it will reveal why mushrooms are crucial to all life on Earth,

and why they have a powerful connection to you and me.

The only place many of us encounter mushrooms is here.

Cultivated edible varieties like these,

are all most of us think about when it comes to mushrooms.

We Brits can't get enough.

It's a multimillion pound business in the UK.

But there's so much more to mushrooms

than this fine example in the fresh food counter.

This mushroom is just one species from an enormous kingdom,

the kingdom of the fungi...

..and fungi are hidden away in all kinds of food products

in this supermarket in ways you wouldn't expect.

Look hard enough and every aisle reveals evidence

of how fungi underpin modern living.

Cheese.

My favourite Stilton cheese, well, it's blue,

and the blue is a fungus.

A lot of fizzy drinks have citric acid in them,

and that's produced by a fungus called Aspergillus niger

in huge quantities.

Many detergents also contain citric acid, just like fizzy drinks.

Ah, here's soy sauce, bread,

Quorn, chocolate, fruit juices.

Well, sometimes they have a bitter taste,

which can be removed by another fungus.

Salmon, red salmon.

The red colour, I'm afraid,

is sometimes due to a fungus called Phaffia.

Some of the protein in pet foods,

which keeps your animals healthy is actually produced by fungi.

And, of course, booze.

The fermenting activity of Saccharomyces,

turning sugars into alcohol.

Clearly, our supermarket shop just wouldn't be the same without fungi.

They're hidden away in all sorts of ways in the products.

They must have a series of special biochemical tricks up their sleeve.

But how exactly is it that they seem to turn up everywhere

and affect so many parts of our lives?

To begin to answer that question, I'm going to a place

where I encounter fungi in all their forms.

Head out into any woodland like this one in the Scottish Borders,

and if you look hard enough,

you'll start finding them everywhere.

To me, they're fascinating.

Some may think they look like any other plant,

but in fact, they're a different organism altogether.

Fungi evolved as a kingdom in their own right,

distinct from plants and animals,

over one and a half billion years ago.

It's thought that in variety,

they outnumber plants by at least ten to one.

And searching for them is my favourite pastime.

Some people might think of autumn as a rather gloomy time of year,

but for me, it's pure joy.

I can take my basket, I can go into the woods...

..and I can do my mushroom foraying.

I've been doing it for decades.

What's the thrill of it?

Well, to the left of the path, to the right of the path,

dozens of different kinds of fungi are erupting.

But, I suppose, the most primeval feeling, the basic one,

is still the thrill of discovery, the thrill of the chase.

You may not realise that what we call the mushroom is, in fact,

just one type of fungus.

It's the form that we are most familiar with

and it's certainly the easiest to recognise.

The head of a mushroom is its cap.

And many have a stalk.

Look underneath the cap,

and you'll often find a set of sharp ridges known as gills.

Ah-ha!

Well, now, this is, of course, the archetypal mushroom.

It's the one that the gnomes sit on top of.

It's the fly agaric.

I can see other species really, really close to hand.

This is the king of the edible mushrooms, the cep,

the penny bun,

porcini.

The fact that it's got so many names is a measure

of just how highly regarded it is as an edible fungus.

It's one of the best.

'But as well as the quintessential mushroom...'

Bit hazardous.

'..if you look a little harder, you'll find a host of other fungi

'that don't look like mushrooms at all.'

Ah, well, now, here's something completely different.

Perhaps doesn't look like a fungus at first sight to people.

It's one of the coral fungi.

This is an ear fungus.

They're still fungi but they're very, very different sort of fungi.

Yellow brain fungus.

Doesn't look like anything from this Earth, really, does it?

It's the beefsteak fungus.

And you can see why - it looks a bit like raw liver.

'In fact, this organism can take so many weird and wonderful forms,

'knowing what it is you're looking at

'can sometimes be a challenge, even for an experienced forayer like me.'

Wow, now, that is something really weird.

I'm not quite sure what's going on.

It's absolutely extraordinary. That's one coming back to the lab.

Almost every foray I go on, I find something new and intriguing.

Time to take a closer look at exactly what's in my basket.

This is our specially-built mushroom lab

where I'll be unlocking the mysteries of fungi

with the help of mycologist Dr Patrick Hickey.

Well, this is quite a set-up you've got here.

Their first secret is their identity.

So here we are with our haul back from the woods,

and what a variety we've got in the basket.

Of course, we notice things like the colour, of course.

The smell.

Oh, yeah, that's got a really sweet smell to it, very sweet odour.

So fungus identification uses all your senses.

It's a very sensory experience.

But there's another way we can really narrow down

the mystery of a mushroom and positively identify it

and that's by doing something called a spore print.

Every mushroom has its own unique spore print

and to do a spore print, we cut the stem off,

and then place the cap onto a piece of paper

and just leave it for a few hours.

When you come back and lift it up,

you'll see the mushroom has deposited a layer of spores

and they look just like fingerprints.

It's a bit like taking a fingerprint from a mushroom.

These spores are like the seeds of a mushroom

and the patterns they create can reveal some surprises,

even when two mushrooms appear to look the same.

So here we've got two similar looking...

-Almost the same, yeah.

-..white mushrooms,

but reveal the spores - one's startlingly white

and the other's very black.

Yeah, it's a key in the identification of the mushroom.

So we have such a variety of colours.

We've got a sort of purple here.

We've got cream, we've got white,

-very pure white, rust brown, even pinkish.

-Yeah.

And I have to say what a beautiful pattern it makes too.

I mean, aesthetically, extremely pleasing.

They're wonderful. They're just like the silhouettes of a mushroom,

and that colour of the spore print is unique to that type of mushroom

and they don't change throughout the mushroom's life cycle.

The spore prints reveal

that mushrooms are more varied and complex than they might appear.

Their world is mysterious and little known,

yet they have the power to affect our lives in unexpected ways.

One of the most striking displays of that power

takes us to the most unlikely place.

This is Mark Gilchrist, a consultant pharmacist

at St Mary's Hospital, London.

He spends much of his day administering and prescribing

the most widely-used type of drug on the planet -

antibiotics.

Antibiotics are tremendously important

in our fight against infection.

Up to about 30% of patients within a hospital setting

can be on antibiotics at any one time

and that's used to treat things like pneumonias

to simple skin and soft tissue infections

and prevent surgical site infections post operatively.

The invention of antibiotics has been a game changer

for medicine and mankind.

And we owe it all to fungi.

In 1928, scientist Alexander Fleming

was carrying out research at St Mary's.

He was studying the staphylococcus bacterium,

and left some samples on his desk, before heading off on holiday,

expecting them to grow and develop while he was away.

When Fleming returned from his holiday to resume his research

on bacteria here in this lab,

he noticed something extraordinary.

His bacteria samples were dead.

They had been completely destroyed by fungi.

Intrigued by why this had happened,

Fleming examined his samples further.

He realised that a fungus spore, possibly from a lab below,

must have landed on the gel plate and germinated.

The spore had rapidly started to feed on the contents of the dish,

starving and ultimately killing the bacteria.

The significance wasn't lost on Fleming.

This could be a new way to fight bacterial infection

inside the human body.

His discovery led to the creation of the world's first antibiotic -

penicillin.

And it only happened thanks to some tiny spores from a fungus,

carried on the breeze.

But to understand how those spores came to be there at all,

we need to delve deeper into the secret world of fungi,

right back to the start of their life cycle,

to the moment a new fungus begins.

I've come to Scotland

to see something I've always wanted to see but never have,

although I've rehearsed it many times in my mind's eye.

This is one of the largest mushroom farms in the UK,

and inside each of these polytunnels,

there's a spectacular natural phenomenon taking place -

the birth of fungi.

It's a magical process, normally invisible,

but tonight I'm going to see it clearly for the first time.

Well, to a mushroom person, of course,

this is like being in heaven,

and everywhere you look, it's extraordinary -

this laser torch picks out little white specks.

They're so numerous. This is like shining a beam

up into the Milky Way.

Billions upon billions of spores in the air all around us,

and they're ubiquitous, so they're going up to the ceiling

they're going out the door,

they're doubtless going into my lungs.

If you want a graphic demonstration of how prolific mushrooms are,

here it is.

So this is how most fungi begin life.

The mushroom spews out many millions of spores every hour,

for as long as it remains above the ground...

..each of them carrying the potential to be a new fungus.

It's mesmerising to watch,

but I want to know exactly what's going on here

and to do that, I'll need more than a laser light.

Back in the mushroom lab,

Patrick can reveal the hidden mechanisms of mushroom birth.

A mushroom, also known as a fruiting body,

really is just the reproductive structure of a fungus

and its sole purpose is to produce spores.

So to look at these in more detail,

what I'm going to do is take a very thin section

through this mushroom cap

and put it onto a microscope slide.

There we go... Ah!

That's the business, isn't it?

Yeah, so the large cylindrical kind of clear part of the cell

is the basidium and those little spiky bits protruding from it

are called the sterigmata and they hold the spores in place.

Now, eventually, when those spores are fully ripened,

they'll drop off into that air space between the gills,

and fall down from the mushroom.

That whole structure, including the spores,

is about the width of a human hair, and, remember, these gills

are packed with them. They're completely lined with a layer

of these basidia continually producing spores.

It's a production line.

It's an extraordinary thought, isn't it? This tiny object,

just a few thousandths of a millimetre long,

contains the potentiality for a new mushroom colony.

Exactly.

This constant production line, forming and releasing spores,

is exactly what I saw so vividly in action at the mushroom farm.

But that's just one way mushrooms can spread their spores.

Others do it in a completely different way.

This is an orange peel fungus,

and it's part of a large group

that fire their spores vertically, with explosive results,

as we can see here when the action is slowed down 600 times.

Oh, look at that!

They're like geysers erupting.

The spores are incredibly prolific. Throughout the course of a day,

each fungus might be capable of producing over a million spores

and over the lifetime of that fungus,

we're into tens to hundreds of millions.

Well, that's extraordinary footage. I've never, ever seen anything

so graphically displaying the way fungi get rid of their spores.

It's a truly impressive fungus.

These fungi can reload and fire time and time again,

often for many days on end.

And how that works

was a brilliant discovery made by someone you wouldn't expect.

Beatrix Potter is famous for penning The Tale Of Peter Rabbit,

but what's less well known,

is that she was one of the leading mushroom biologists of her time.

Both Potter and pioneering biologist Arthur Buller

spent much of their lives trying to find out

how some mushrooms release their spores.

They discovered that a tiny drop of fluid,

now known as Buller's drop, forms at the base of every spore.

As the spore ripens and begins to detach,

the Buller's drop fuses with a second tiny water droplet

that forms at the side of the spore.

Like two raindrops joining together on a windowpane,

this fusion causes a rapid shift in mass

that dislodges the spore in such a spectacular fashion.

This microscopic process all takes place

in a few millionths of a second

and is key to how many fungi reproduce.

But of them all, there's one particular species

that's a record breaker.

You may think that the fastest organism on the planet

is a cheetah or maybe a peregrine falcon,

but you'd be wrong.

Allowing for scale, the speediest organism on the planet

is actually a tiny fungus.

It grows on top of cowpats.

It's called Pilobolus crystallinus, or the "Hat Thrower" fungus,

and no other species demonstrates better

the importance of the spore release mechanism.

This little fungus feeds on the dung of herbivores,

but when the supply of nutrients from one pile has been exhausted,

it needs to move on,

and to do that, it has to get out of the dung

and onto new blades of grass.

That's the equivalent of you or I

trying to throw a tennis ball over the Eiffel Tower.

But, then, you or I can't do this.

BANG

MUSIC: "Zorba's Dance" by Mikis Theodorakis

Using water drop acceleration, these spore capsules,

seen as little black hats, can be fired at a speed

of up to 40mph in just two millionths of a second,

pulling an astonishing 20,000 Gs in the process.

BANG

The little "Hat Thrower" fungus is a wonderful example

of the sophistication of fungus evolution.

It throws its spore body more than a thousand times its own length

into clear grass, away from cowpats,

so that the cows will come along, graze the grass,

incorporate the spores and so propagate another generation.

The "Hat Thrower" shows just how ingenious fungi are

when it comes to reproduction.

They will go to extraordinary lengths to ensure their own future.

It's the key to why fungi have become such a dominant life form

with such vast numbers of species all over the planet.

And it's certainly a talent to which humankind owes a great deal.

But as impressive as spore dispersal might be,

it's just the beginning of the fungus's life story.

It's the next stage that truly reveals why they are

so vital to all life on Earth.

So far we've just been looking at the fruit body of the mushroom.

Indeed, I suppose to most people they think that IS the mushroom.

But it's only part of the story.

To discover how mushrooms relate

to so many other organisms on our planet,

we have to go further, we have to go underground.

You'd be forgiven for thinking that what we see

above the ground is the main part of the fungus...

..but, in fact, the vast majority of the organism is hidden underground.

It's a huge web of tiny threads, spreading out in search of food.

And the only way many fungi can get what they need,

is by attaching themselves to other organisms,

and engaging in a two-way exchange of nutrients.

It's a process that results in one of the most complex,

yet crucial relationships in the natural world.

To discover how this works,

I'm meeting Kew Gardens mycologist Bryn Dentinger.

Anywhere from 70% to 90% of all plants on Earth

will form a very special intimate relationship with fungi

and the fungi will attach themselves to the plant roots,

either directly penetrating the roots

or sometimes they will form sheaths on the outside

that will envelop the root like a kind of glove.

This is where the nutrient exchange takes place

between the fungus and the root.

This nutrient exchange works both ways.

The fungus feeds on sugars from the plant that it needs to grow

and in return gives back water and minerals

that the planet is unable to absorb enough of itself.

I'm going to lift up this pine seedling here

and you can see, where I'm pointing with my pinkie, that white fuzz.

Oh, yeah, OK.

Those are the fungal filaments

and it is completely covering the roots of this pine tree right here.

And it extends over a much larger surface area

than the roots can possibly cover,

and this gives them access to all kinds of nutrients

and water, even, from the soil,

so they can extract nitrogen and phosphorous, in particular,

from the soil,

and provide those to the plant,

which the plant will then exchange for sugars

that it produces through photosynthesis.

And the two together make for a better plant?

A better plant and a better fungus, healthier soil.

So it's a win-win situation for both?

It's a win-win situation for both partners

and, in fact, for the entire world.

'We're going to look for evidence of this vital relationship,

'in the wild.'

Well, we can't see them,

but, all around us there are these unseen fungal partners.

They're invisible to us when we just take a nice stroll along a path,

but they're all around us.

-Shall we have a go?

-Let's do it.

I think I've got some.

Well, I mean, you don't have to search for it.

-You can see the white tips here.

-It's very obvious, yeah.

But every one of these tiny little, side-branching roots

is covered in fungus.

There's a fascinating and fundamental relationship

between fungi and land plants,

not just here in Kew and every park in Britain, but in every field.

Without this relationship, plants couldn't thrive.

It's impossible to overstate its importance.

So how exactly does this hidden process happen?

To find out, Patrick has been capturing it in action,

starting from the moment a spore hits the ground.

The primary mission of a fungal spore is to feed

and find food resources.

Now, under the right conditions, the spore starts to germinate and grow.

That's what we can see here. We've placed some spores

into a drop of water and as you can see, they're starting to swell.

There's a little bit of movement starting to go on inside.

-Oh, yeah.

-And already you can see this little bud emerging,

and that little bud is the beginnings of a fungal hypha.

So, what is a hypha?

The hypha is the feeding part of a fungus, the feeding tube,

and the hypha goes in search of water and food

and will continue growing and branching

until it eventually establishes a colony, a fungal colony.

Does it grow very fast?

Once a hypha finds its food source, it can develop very quickly

and form what we call a mycelium.

A mycelium is the scientific name for the fungus's feeding network.

Here magnified 500 times,

we can see one starting to form as many hyphae begin to web together.

Essentially, it is a fungus's root system,

a complex series of feeding tubes.

It's not unlike a microscopic human digestive system,

processing food that allows it to grow.

Within these tubes are the nutrients that are a fungus's entire future.

And you can see the network forming now.

Yeah, and this is in the centre of the colony.

You have this branched network that keeps on feeding nutrients

through the colony and sharing its water and resources.

And that's only half a millimetre square?

Roughly half a millimetre is the sort of field of view

that we're looking at here

and it's very much like a road network -

we've got these kind of main motorways,

we've got lots of little side routes in there

and we've got flow of nutrients, water and it's very dynamic.

For example, if I was to break one of these tracks,

the fungus would very quickly adapt and form new connections.

-And form new connections and new routes.

-Mmm.

It's extraordinary how bustling it is.

Of course I can now see what we saw with Bryn Dentinger -

how efficient these hyphae are at gathering nutrients

and moving through the soil.

Absolutely, and even in the most dry soil environments,

fungi are able to draw up the moisture from the soil

and transfer it into the plants through this co-operation.

It is extraordinary, extraordinary footage.

Although the mycelium is almost entirely invisible to us,

it makes up the vast majority of the organism.

And its size can be truly breathtaking.

So big, in fact, it can often extend for miles.

The biggest organism in the world is not the blue whale,

but a mycelium that spreads across an incredible 2,384 acres

in Oregon's Blue Mountains.

It's called Armillaria mellea, or the honey fungus,

and this example is thought to be over 2,000 years old.

It's a mind-boggling example of how far a mycelium can grow.

But it also reveals just how destructive a feeding fungus can be.

These are clumps of honey fungus.

It's the same fungus that spread inexorably

through the forests of Oregon

and it demonstrates a very different, some would say sinister,

relationship between mycelium and trees.

Unlike the balanced nutrient exchange

that we see between most fungi and their plant partners,

honey fungus takes much more from its host than it gives.

It consumes all the sugars it needs,

but crucially doesn't give back enough water and nutrients

to help the tree grow properly.

As a result, the greedy mycelium of this fungus thrives,

while the tree slowly weakens.

Honey fungus is a slow killer.

It advances from tree to tree on hidden threads.

As our tree population ages and some sickens,

the rise of honey fungus is inexorable.

But it's not the biggest threat to our plants and trees.

There's another species of fungus whose hunger is even more deadly.

I've come to Norfolk to find evidence of a fungus

that's very difficult to see,

but whose eating habits

are threatening to wipe out one of Britain's oldest trees.

Just a few years ago, a new killer arrived in Britain -

ash dieback disease,

or Chalara fraxinea, to give it its scientific name.

And no fungus better demonstrates

the greed of mycelium for nourishment...

..and if it has its way, maybe,

magnificent forest trees like this ash

may yet become just a part of history.

David Bole knows all too well

just how destructive this fungus has become.

And there's quite a lot of dieback in here, isn't there?

Yeah.

This is one of the first woods where we discovered it.

What we're finding now is that there's over 500 cases

in the wider environment and as we do more in-depth surveys,

more and more cases are coming to the fore.

Take me through the symptoms.

Well, the first thing to look for is this, the black leaves,

which we've got here

and we've got a really good example on this little, young tree here.

The leaves have died but they're black.

They really don't look healthy and they're hanging onto the tree.

I notice they die from the top too,

so they're dead up here but still green down here.

Yes, you know, it's called dieback and that's a good way

to think of it - we have the tree slowly dying back.

Other symptoms are these diamond-shaped lesions.

The fungus lands on the leaves, the mycelia come in,

and works its way up and down the cells of the tree

and forms these very particular diamond-shaped lesions.

This process is rather eerily called necrotrophy,

which means eating the dead.

The feeding hyphae of ash dieback

attach themselves to their tree hosts

in the same way as other fungi,

but they obtain their sugars without providing any nutrients

or water in return.

It's all one-way traffic

and has a fatal outcome.

OK.

OK, so let's just have a look inside.

Oh, yeah. You can see discolouration.

It's absolutely patent.

So the disease has entered here and this is the fungal mycelia,

which are starting to work its way inside the tree.

The mycelia get inside all the cells

that transport the water up and down the tree

and stop the water transport

and so the tree effectively dies of thirst, if you like.

It's a sad end to one of our most beautiful and elegant forest trees.

It really, really is, yes.

I mean, we'll probably lose a generation of ash

but let's hope we see that coming back.

Ash dieback demonstrates just what happens when the delicate balance

between plant and fungus gets out of kilter...

..and that's what allows this disease

to spread so far and so fast.

It also shows just what a voracious eater fungal mycelium can be.

But though this unstoppable appetite

can be deadly in the natural world,

some scientists are looking to turn it to our advantage.

This is Eben Bayer, an entrepreneur based in New York.

He noticed something intriguing that happens

when some mycelium spreads out in search of food.

First time I saw mycelium in action was holding

clumps of woodchips together on my family farm

and rather than falling apart,

they'd be held together by these white fibre strands.

One night, sitting at home on my futon in my apartment,

I got this crazy idea about, "Hey, mycelium seems to grow,

"and glue the forest floor together.

"Maybe we can use it as a glue."

Eben saw huge potential in this binding property of mycelium.

He used it to create a new kind of packaging,

one that he believes could, ultimately,

become an eco-friendly alternative to some plastics.

Just in packaging alone, there's like billions of dollars

of Styrofoam used every year,

somewhere between 3.5 and 5 billion of styrene,

and the biggest issue with plastics is at their end of life

and with our material, you get something that,

at the end of its useful life, can be composted, right.

Your packaging becomes a nutrient for your neighbourhood, not a pollutant.

To make his new material, Eben mimics what happens in nature.

He takes some ground corn stalks and seeds them with fungus spores.

The spores germinate, and begin to feed on the stalks,

breaking down and digesting them, so the mycelium can start to grow.

The mixture is then placed inside a mould and left

for the mycelium to perform its biological magic.

So, they'll sit on a rack like this for anywhere from 24 to 72 hours.

It doesn't look like anything's happening,

but the mycelium is already going to work,

growing and extending out from every one of these particles

and building a strong, tough network.

And within 24 hours, this part will look a little white

and that's the mycelium gluing everything together.

So this is a finished corner block.

It's been grown in our production process, it's been moulded

and all of this came from that loosie-goosie agricultural by-product

you saw at the beginning.

Pretty incredible, huh?

What we've done with mycelium here,

which is basically leveraging a living organism

to create really great technology,

is where the excitement is, that's where the innovation is

and that's where the solutions are going to be for the next 100 years.

So the mushroom mycelium could help us tackle the global problem

of plastic waste.

But Eben's work also demonstrates another important trait

of the feeding mycelium.

While some fungi feed on living organisms,

others only eat those that are dead.

These fungi are able to break down and digest organic waste

and in doing so, recycle it.

This process is called saprotrophy

and it's absolutely vital in the natural world.

In this damp wood, the litter of leaves,

indeed, every twig, is being consumed by mycelium,

that breaks down the cellulose and other compounds.

Even...

Even wood can be digested by fungi.

The hard lining that gives the wood its strength

can be consumed and the wood reduced to little more than rubble.

Were it not for the relentless activity of mycelium, in fact,

the whole planet would be covered with a mass of undigested scrub.

It's hard to overstate the importance of saprotrophic fungi.

They have successfully recycled the world's natural waste

for hundreds of millions of years,

making entire ecosystems habitable for animal and plant life.

So how do they achieve this crucial trick?

So, Patrick, let's talk rot.

Few people realise just how important

those saprotropes fungi are in nature.

How does it work?

Well, fungi are really quite invasive.

The fungi have this mycelium, which penetrates deep into the waste

and unlike us, where our stomachs are internal,

the fungi secrete their digestive juices out into the environment

and start breaking down the complex molecules,

things like cellulose, into more simple forms.

This is via a myriad of those little hyphal threads.

That's right.

And to demonstrate just how effective saprotrophic fungi are

at breaking down organic matter,

I've put several days of kitchen waste into this beaker

and I've filmed it over two weeks

to see just how quickly it goes down, it rots down.

SQUELCHING

So there it is, just sort of sinking down.

Yeah. Lots of juice exuding from the vegetables.

So the invisible threads of the mycelium are getting in there,

breaking vegetables and the other organic waste,

into something they can use.

The other important thing to note here

is that when all these vegetables did go into the beaker,

they already had spores on them, so they were already pre-seeded

-with the spores.

-Because spores are everywhere.

Exactly, when you bring the food back from the supermarket,

it'll already have a coating of a whole cocktail of different spores

and as soon as those fungi are in a slightly warm environment,

it becomes quite a feeding frenzy, if you like.

So, Richard, I'm going to show you the results of the one

that I prepared two weeks ago.

Well, it couldn't be much clearer than that.

Yeah. Look how far it's gone down. This was the start point and...

At least a third.

..it's gone down about a third and I'd expect, within another two weeks,

to be almost to the bottom.

If this process wasn't happening

we would just be surrounded by organic waste matter.

-Heaps of vegetables.

-Exactly.

What it does show is just what makes the fungi

such efficient seekers after... scavengers after nutrition.

Yep.

Extraordinary.

The brilliant way the mycelium of a saprotrophic fungus

uses digestive juices just like humans to break down waste

makes it a recycling machine like no other.

And it doesn't stop there.

For as saprotrophic fungi recycle organic matter,

they're performing a key role in creating healthy soil,

soil that can, in turn, sustain new plant life

and that's also a home for a host of other life forms,

tiny micro-organisms that live within it.

And for some fungi,

the arrival of these new guests is just another feeding opportunity.

These oyster mushrooms, or Pleurotus,

have mycelium that breaks down the wood in rotting logs.

They're quite efficient at doing this,

but they have a shortage of one essential element, nitrogen

and to make good this deficiency,

they've evolved a very special trick.

From the end of some of its hyphae,

the oyster mushroom emits tiny lassos

that secrete a powerful toxin.

And it does this for one reason...

..nematode worms.

These tiny organisms live within the logs

and happen to be rich in the nitrogen

that the hungry mushroom needs.

The oyster mushroom lures the nematodes towards their tiny lassos

before enveloping them.

Once trapped, it's curtains for the little worm,

and dinner for the mushroom

as it gets the nitrogen-rich fluid it needs.

The oyster mushroom's rather gruesome feeding trick

demonstrates yet again just how sophisticated a fungus can be

when it comes to getting the food it needs.

It's a talent that, once again, we humans are looking to harness.

Over in Washington State, mycologist Paul Stamets

has turned to our hungry friend the oyster mushroom,

in the hope he can use it on a truly grand scale -

to tackle some of our most pressing environmental problems,

such as chemical pollution.

One of my great realisations in life is that habitats have immune systems

just like we do,

but mushrooms are the bridges between the two.

These things unravel and break down large molecules into smaller ones

that are very useful for other members in the ecological community.

The course of that decomposition, has many different properties

that we can use for breaking down toxic waste.

That looks good.

Paul discovered that mushroom mycelium

can break down the hydrocarbons present in much chemical waste.

It's a process he calls bioremediation.

The mushroom is greedily eating the pollutants away.

It looks convincing in the lab,

but does it work in practice?

Paul's theory was recently put to the test on an industrial level

when a heavily-polluted petrochemical site

was seeded with oyster mushroom mycelium.

The work was carried out by environmental engineer

Howard Sprouse.

Yeah, bring her down a little for me.

After just two days, the team found that their polluted pile

had been transformed by the mushroom mycelium

and was now teeming with new life.

Well, this is interesting. We've got lots of worms in here now.

That's a good sign.

If it drops any more, we're going to be able to use this soil anywhere.

The contaminate has gone...

..the decomposition process that the fungi have started

is continued by other soil microorganisms

and you end up with soil that's richer than it was when you started.

Paul's study shows that oyster mushroom mycelium

can not only digest chemical waste -

it also manages to create an entirely new ecosystem

in the process.

At a time when the Earth is suffering from toxin exposure,

erosion of habitats, overpopulation,

deforestation, loss of soil integrity...

..mushrooms present themselves with unique properties

that can address all those problems with a single group,

and that's what I find so exciting -

that the solutions are literally underfoot.

Paul's work shows just how great

the potential of fungus mycelium might be.

Its hidden underground threads act upon their natural environment

in truly remarkable ways we are only now beginning to realise.

But as vital as it could be to us,

the mycelium's feeding quest has one simple goal...

..to produce its fruiting body...

..bringing the organism to the end of its life cycle.

We've seen how mycelium can form complex feeding webs

and how the mycelium underpins so many of Earth's ecosystems...

..yet that mycelium itself has only one purpose...

..to fulfil its own life cycle and to lead once again to the mushroom.

For the fungus, this final stage simply means reproduction

and the dispersal of billions of spores.

'But for another species,

'it's just the beginning of its relationship with fungi.'

Nice find.

'And that species is us.'

Ah.

The sulphur tuft.

Very abundant.

Very inedible.

'Its mythical status in folklore and magic

'has made the mushroom an object of both fascination and fear.'

Well, now, this is a troublemaker.

'And sometimes that fear can be for good reason.'

Poison pie is, as its name suggests, not a good thing to eat.

Go out into any woodland

and you're likely to encounter a wide range of poisonous fungi

that you certainly would not want on your dinner plate.

People get a big nervous about this one...

the Sickener.

Well, the name tells you everything. You don't want to eat it.

The notion that fungi can be poisonous

is what frightens us most about them.

This is the most poisonous mushroom known to man.

It's the death cap.

People have eaten it, apparently in mistake for a field mushroom.

I can't think how.

But they'd have cause to regret it, because half a cap of one of these

is enough to kill a grown man,

and slowly,

and painfully.

I've been a field mycologist for many years

and know to avoid dangerous mushrooms like the death cap,

but their toxicity does raise an interesting question -

what is it that gives mushrooms the power to kill?

To explore this, I've come back to the lab once final time.

Every fungus will have a cocktail of different chemicals within it,

and depending on what type it is, there's various different types

of poisonous chemicals which are present in these mushrooms.

Possibly one of the worst ones is something like the destroying angel.

Or the death cap, which is its close relative.

Or the death cap, and those have a substance called amatoxins,

which are deadly toxic.

You'd only have to eat one or two of these to be completely poisoned.

You'll end up with liver failure, kidney failure and death

and it's a really quite nasty way to go.

So we know that mushrooms are toxic, but why are they toxic?

Well, there's a theory that mushrooms evolved to become toxic

in order to discourage predators from eating them,

but I'm not sure that's exactly the case,

so I've set up a little test with a selection of mushrooms

and we've brought in a guest to do the test for us.

Patrick has offered a selection of five mushrooms to a hungry slug,

one of which is poisonous to humans.

But which will it prefer?

After a look around and having a nibble of one or two,

he seems to have settled on this one.

Oh, the sulphur tuft, which is famously bitter and poisonous.

Yeah, it doesn't seem to bother the slug

and, in fact, he seems to be having a tasty meal on the gills, there.

So what we've seen is certainly not in support of the idea

that fungi are kind of protecting themselves from being eaten

until mature. In fact, you could argue that that mushroom

actually wants to be eaten,

so what's it all about?

I think, really, the bigger picture

is the diversity within the fungal kingdom,

in that the fungi produce thousands of different chemicals

and it just so happens that some of those are toxic to us,

whereas they might not be toxic to something like a slug or an insect.

In fact, it may be a very important food source for those animals.

So you've just got a huge spectrum of different types of chemicals.

And we're only just beginning to explore

-the implications of some of these.

-Absolutely.

We don't yet fully understand why some fungi

have such a potent effect on us.

More research is needed.

But, already, we're beginning to exploit

some of their seemingly sinister behaviours for our own benefit.

Can I introduce you to cordyceps?

These are dried specimens of a very famous fungus,

famous in Chinese medicine for curing all manner of ills.

It's a curious fungus with a strange, parasitic lifestyle.

Unlike most fungi, it doesn't feed on dead matter

but instead seeks out a very different host.

Like something out of science fiction,

this fungus grows inside insects,

slowly killing them until the fruiting body is ready to emerge.

But despite its rather, alien life habits,

the chemicals concealed inside the cordyceps

may yet prove crucial to a major medical breakthrough.

Doctor Cornelia De Moor from the University of Nottingham

is using this little mushroom in a cutting-edge treatment

for one of our most feared diseases -

cancer.

So in cordyceps there are very high levels of this cordycepin.

And cordycepin is a compound

that is actually only very slightly changed

from a very common compound that you find in all cells called adenosine.

It's only one oxygen difference.

But for some reason, only cordyceps fungi make cordycepin

while all organisms make adenosine.

This unique compound produced by cordyceps has long been of interest

to alternative medicine in the treatment of cancerous tumours.

But how it worked was never clear and Cornelia was keen to find out.

What surprised us immensely the first time we treated cells

with cordycepin is when we put cordycepin on cells like that,

they changed shape into cells like that

in which the little grains are gone and the cells start to shrink.

So when we saw this,

we knew there was something quite fundamental happening to the cells

and that then led to our later discoveries

on the affects of cordycepin.

Cornelia knew that with any cancer,

in order for the individual cells to multiply and grow,

they must join themselves together

using tiny stems called poly-A tails.

And it's here that she has discovered that cordycepin

plays a crucial role.

So we've been doing some work on breast cancer cells,

which we've been treating with cordycepin,

and what we're seeing is that the cordycepin appears to stop

the making of the long poly-A tail.

So it might not kill the cell

but the most important thing - it stops the growth of the cancer cell,

by cutting off the machinery that is necessary for cell growth.

It is a completely new mechanism for a cancer drug,

so all other cancer drugs work on completely different principles,

not on inhibiting this polyadenylation,

so it could be the first of a new class of drugs,

not only for cancer, but also for inflammatory diseases.

Medical breakthroughs, from Fleming's penicillin

to cutting edge cancer research, reveal an extraordinary truth.

The cells of fungi have the ability

to interact with our own cells on a profound level...

..to alter them in ways that affect our health, even our survival.

And this is a powerful clue

to the true relationship between fungi and us.

Time and again, we seem to discover deep biological connections

between ourselves and the fungi.

But what could we have in common with a mushroom?

To find out the answer, we have to delve deep

into our own evolutionary history.

As we've seen, fungi are neither plant nor animal.

Early in the story of life on Earth,

they established themselves as a kingdom in their own right.

But it's the moment when this happened that is truly significant.

At the point when plants and animals diverged,

the fungi were still part of that animal branch.

It was not until about ten million years later

that they began their own evolutionary journey

as a distinct kingdom.

This explains why they have retained a number of key biological traits

that make them much more animal than plant, much more like us.

Traits we've seen time and time again,

as we've explored their fascinating life cycle...

..from the explosive way that they release their spores...

..to the way they feed and digest other organisms, much as we do.

At every stage of their life,

fungi reveal just how much like us they are.

It's a powerful connection, that explains why we work

so well together.

So we are all much more mushroom than you could ever imagine.

And because of this close affinity, sometimes the fungi work with us,

and even sometimes against us...

..and that is the true magic of mushrooms.