In Our Time - Fungi

Episode Date: February 15, 2018

Melvyn Bragg and guests discuss fungi. These organisms are not plants or animals but a kingdom of their own. Millions of species of fungi live on the Earth and they play a crucial role in ecosystems, enabling plants to obtain nutrients and causing material to decay. Without fungi, life as we know it simply would not exist. They are also a significant part of our daily life, making possible the production of bread, wine and certain antibiotics. Although fungi brought about the colonisation of the planet by plants about 450 million years ago, some species can kill humans and devastate trees. With:Lynne Boddy Professor of Fungal Ecology at Cardiff UniversitySarah Gurr Professor of Food Security in the Biosciences Department at the University of ExeterDavid Johnson N8 Chair in Microbial Ecology at the University of ManchesterProducer: Victoria Brignell.

This is the BBC. Thanks for downloading this episode of In Our Time. There's a reading list to go with it on our website, and you can get news about our programs if you follow us on Twitter at BBC In Our Time. I hope you enjoy the programs. Hello, our planet is home to millions of species of fungi, and the role they plays vital. Without fungi, life on Earth, as we know it, simply wouldn't exist.

They also play an important part in our everyday lives. The making of bread, beer and wine wouldn't be possible if fungi were not a available. In the field of medicine, they've been part of the production of certain antibiotics since penicillin. However, there are other fungi which can cause nasty diseases in humans and destroy trees. Some fungi are even toxic to humans and can kill if consumed. Despite their significance, much of the way in which fungi operate remains a mystery. With me to discuss fungi are Sarah Goer, Professor of Food Security in the Biosciences Department at the University of Exeter, Linn-Body, Professor of Fungle Ecology at Cardiff University,

and David Johnson, N.H. in Microbial Ecology at the University of Manchester. Lin-Body, what is a fungus and what did they look like? Well, fungi are not plants, they're not animals, they're not bacteria. They're a kingdom of their own. You could be forgiven, I suppose, for thinking that they're plants because they're fruit bodies, the things which we think of as toadstools or brackets on trees, I suppose superficially they look a bit like the flowers or fruits of plants. but they're not.

The flowers and fruits of plants, we know that's not the only part of a plant. There's the leaves and the roots and the shoots. And in the same way, the fungus has much more to it than that toadstool that we see when we wander through the woods. The toadstall is just the tip of the iceberg. Underground, we have the main body of the fungus.

The mycelium. Mycelium is a network of fine filaments. That's the body of the fungus. This is what sets fungi apart from all other organisms. It's the living part of the fungus. It grows and it feeds as a network of fine tubes with a large surface area with a huge enzyme capacity. I'm told from the notes that I've been given by the three of you,

that there are about three to five million species of fungi and you've identified only 170,000 of them, something like that. So there's a long way to go. What do they have in common? Well, the vast majority of them have this mycelial structure. Some of them are unicelles, such as yeasts. They have kiting in their cell walls as a common feature, and that's also found in animals, in vertebrates, in their exoskeletons.

So actually fungi are more closely related to animals than they are to plants. How do they differ? They're related animals and plants. How do they differ from them? Can you just develop that a bit? Yes. You've said more or less they're suiagenerous at the start of the programme, then inside, also an inside plant.

So there's a bit of a crossing of lines there. Yes, there is. There's a bit of all sorts of worlds, I suppose. Fungi, in some way, are like animals, in that they have sort of foraging behaviour. They search around for food. They don't get up and wander around like many animals do, but they search for food and when they find it, they respond.

And actually, if you look at some of the patterns that they make, they rather look like the termite trails that you see when termites go investigating for food sources. They're a bit like plants in the sense that they don't wander around. They're just very different. They've got similarities to different organism groups, but they've got huge differences. One of the most important things about them

is that they can't make their own food. So plants make their own food. Fungi can't make their own food. They have to get it in the same way as animals do from other organisms. So that is a crucial feature about fungi. When did fungi scholarship take root? Take root?

Well, I'm not sure what the answer to that is. I suppose people started thinking about fungi and classifying them in the 1700. So Linnaeus, the great Swedish biologist, he was the first person to group organisms and he grouped things into animals and plants, but he threw the fungi into the plant category. So we're in good company when we think that perhaps they look a little bit. like plants and then it's sort of carried on from there

What about Hook and his microscope? I'll pass you over to Sarah for that one. All right, we're going to Sarah. Can I come back to you later then, Sarah? We can talk about Hook with you later. So we've got Linnaeus and classifying and it comes in there. Okay, David Johnson.

What role of fungi played in the history of life on earth? They have a hugely important role and one of the main events that they were responsible for was the greening of the earth. So the movement of plants from the aquatic environment into the terrestrial environment, which happened about 450 million years ago. And that process was only possible because of the role of fungi. So when plants are growing in the aquatic environment,

they have nutrients that are fairly readily available to them in solution. So taking up nutrients is rather easy. On land, that's not the case. And the sort of primitive roots that these early plants had were really not up to the job of acquiring nutrients. And so one of the critical processes was the evolution of the mycorrhizal symbiosis, so the interaction between fungi that live on land with plant roots.

So they developed these very intimate associations that enable plants to colonize the turrets, terrestrial environment and take up nutrients via these root-borne fungi to enable the plants to diversify and form the huge diversity of plants that we see today. This happened about 450 million years ago. It did, yeah, and we know that. We know that because there are some remarkable fossil evidence to show this, and some of that's in the UK, so the famous Riney Church near Aberdeen.

this dates back to the early Devonian. It's about 400 million years ago. And it contains some incredible preserved specimens of these early primitive plants. From 450 million years ago? Maybe slightly younger, maybe 420 million years in the case of the Rhinni church. But they don't just contain the fossilised plants,

but you can actually see evidence inside the root systems of structures that are remarkably similar to the structures that you see in modern day plants. You can see Haifa colonising plant roots and developing the distinctive coils inside the roots. They're all beautifully preserved. So that provides some of the best evidence to date this greening of the earth.

And would you tell us about the range of environments that fungi inhabit? It's more a question of where they don't inhabit. They're literally everywhere. So in this room there are probably fungal spores floating around. What are they up to? Well, they're very tiny. So one of the reasons they're so successful is that the spores can disperse very easily because

they're so tiny and they're produced in huge abundance. So that's enabled them to colonise virtually all areas. But I'm sorry, it's a very simplistic question, but they're floating around here in this room in broadcasting out. Are they looking to do anything or is just an accident? Will they do anything other than float around? And they will find a suitable substrate to colonise and to germinate. Many fungi are associated with humans on their skin, for example.

It's maybe a scary thought, but we are covered in microbes, including fungi. So they're essentially looking for a suitable environment to germinate and to colonise. And that's enabled them to colonize all terrestrial biomes. So the boreal forest, the Arctic, the dry valleys of Antarctica, the tropical forests. Every terrestrial biome contains thousands of fungi. And also the aquatic environment, so particularly freshwater environments, but also the marine environment. So they're really incredibly successful at colonising Earth. And incredibly diverse.

Incredibly diverse as a result of that. Can you give us some examples of the diversity that sometimes they're like this? and sometimes they're like A, sometimes they're like Z. Yeah, so, I mean, Lynn mentioned that some of these fungi produce very distinctive mushrooms, which I think most people are familiar with. So that's one group of fungi that produces very distinctive, but very transient, very short-lived, spore-bearing structures. Not old fungi produce those.

Some produce much more cryptic fruit bodies, so the so-called Ascomycites, which produce, like cup-shaped fruit bodies. And some don't produce fruit bodies at all. So they have very different morphologies, and that's meant that we can classify them in very different ways. Often the early classification systems were based on their morphology. But they also have very different modes of nutrition.

So some fungi are parasitic, some fungi are saprotrophic, so they're breaking down dead organic material to get their nutrients. Some fungi have formed mutually beneficial associations. I mentioned before the greening of the earth. That's an example of the evolution of a mutually beneficial association between the plant and the fungus. So they have very different modes of nutrition. Sarah, you were going to tell us something more about Robert Hook.

So in 1665, Hook, who is responsible for inventing the compound microscope in Oxford, looked down his microscope and the first thing he described were cork cells. Then he picked up a red leather book and he looked at what was growing on it and he described the fungus mucor. He then wandered out into his garden in Oxford and he picked some rose leaves

and on his rose leaves he saw powdery mildews. So his contribution was the ability to see fungi for the first time in 1665 with his compound microscope. How many, can we talk about the species then of fungi? So how many are there? Well, you know the names of perhaps 130, 140,000, as you said at the beginning.

And out there in the biosphere, there may well be between 2.8 and 5 million other species that we don't yet know about. So a huge biodiversity. And who's, are you all three of you and friends of your colleagues on the case of trying to discover those and categorize those, classify them? There are many people in the world looking at classification and building trees, so family trees, of relatedness between fungi and the animals across the world. But my particular interest is in fungal diseases of crops. So there are many scientists doing these sorts of things, but not me. So what are you finding out about the fungal diseases of crops

that we ought to know and be aware of? So I think if you look at the balance of disease in humans, we are rather obsessed with getting diseases caused by bacteria and viruses. But in plants and in crops, the number one agent of plant disease is actually the fungi. So fungi are number one and backerine. bacteria and viruses and nematodes cause diseases, but they're not as important. So in terms of crop diseases, at the moment, despite the fact that we spray our crops with

fungicides and we breed disease resistance into them, we're still losing between 10 and 23% of our crops per annum to crop disease, and we're also losing up to about 20% after harvest, so post-harvest storage diseases caused by fungi. And so food security is hugely challenged by the march of fungi across the world, not only by trade and transport, but also due to climate change. People listening will know about a mushroom. Can you tell us how that is a fungus? Yes, so for me, defining a mushroom is rather like looking perhaps at the London eye and say the London eye is London. A mushroom is just one small part of the kingdom of fungi. What it represents, as David said, is the fruiting body. So the ability of this particular creature to put

up something that looks a bit like an umbrella and from the bottom of the umbrella where the gills are to release thousands upon millions of spores to make sure that the next generation of mushrooms or jelly molds or rust and smuts occur. So this is one part of the fungal kingdom where it makes a fruiting body and it disperses its spores. But that part of the kingdom of fungi is only one very small part, perhaps 11% of the fungi that we currently know. And how about these peri circles? Fairy suckers are also caused by these sorts of fungi, which grow not only by producing the fruiting bodies, but they grow out from a central point by raiding out as these long threads of filaments that Lin described the mycelium under the grass.

And can I come back to you? Can we develop the idea of why they're so crucial to plants, please? Yes, certainly. I think there are quite a lot of reasons. Firstly, they form this relationship called mycorizers, which Dave has already explained. for the greening of the earth, and that's where the fungus associates with the roots of plants. So mycorrhizer, it's from the Greek, literally, mycos means fungus, rhizor means roots, so literally fungus root. So the fungi associate with the roots of plants,

probably getting on for 90% of all the plants that we see in nature have these associations. The fungi spread out, their fine filaments into soil, they absorb water and mineral nutrients, and they give that water and those nutrients, to the plant. They also protect the plant roots from pathogens that are in the soil. And as a swap for this, the plant pays by giving the fungus sugar. So sort of exchange is no robbery. It's a mutualistic relationship. Vast numbers of plants have these, as I say, 90%. Second reason is

that fungi are the garbage disposal agents of the natural world. They're the decomposers. They break down the dead stuff. If it wasn't for fungi, we'd be up to our armpits in dead stuff. And I suppose that's not probably the real issue. The point is that in all of that dead plant material, there are nutrients locked up inside. And by breaking down that dead material, fungi released those nutrients and they're then available for plants to carry on growing. So that's two of the main reasons why plants absolutely depend on fungi. And indeed, our planet depends on fungi because they depend on plants. Fungi are also intimately related to plants.

In another sort of way, there are these fungi called endophytes. So endophyte literally means endo within fight plants, so fungi within plants. And if you look around you, every plant you see has fungal endophytes inside in the leaves and the roots and the shoots. They're just very, very, very tiny little tiny, just a few hifie here and there.

But they're interacting with the plants. They're not showing any symptoms. The plant doesn't look ill or anything. doing bad things, but they're in the plants. And in fact, lots of them confer important properties to the plants. So fungi often make chemicals which are inhibitory to other animals. So some of these endophytes are making nasty chemicals which deter grazers. So these could be grazers like aphids or insects or indeed bigger animals. There's a situation with horses sometimes. that eat rye grass that have got these fungi in them

and they stagger around as if they're drunken and it's to deter the horses from eating the grass but it's the fungi that are producing those chemicals other fungi give plants the ability to colonise very saline soils so these endophytes are very important too and then of course the fourth reason why fungi are important to plants is sort of the negative side that Sarah's already alluded to, and that's when fungi are pathogens, killers of plants.

David Johnson, can we develop the idea of the different sort of fungi? Yeah, so I think the modes of nutrition are a good way to start. So, I mean, we've talked about parasites, sapatrophes, and neutralisms. So that's a nice way of grouping fungi away from the classical taxonomic approaches. So, for example, the sapatrophes, they're breaking down organic matter. They're using energy locked up in that dead material to gain their energy, to gain their carbon and their nutrients. Linzol also mentioned the mycorrhizal fungi, which are dependent on plants for their sugars, and in return provide plants with mineral nutrients.

And then there's the parasites which are doing harm to their particular host organism. So, for example, there's a group of. parasites that colonise ants, which produce mind-altering chemicals in the ant's brain that forces the ants to crawl up onto the top of plant leaves, hook themselves onto the leaf where they die, and then the fungus can produce its little fruit bodies and disperse from the ant. So it's a remarkable adaptation as a strategy to gain a source of nutrients, which is the body and to gain a suitable site to disperse their spores. I asked you about the beginning of the serious study of fungi.

Can you mention Linnaeus. Can we say how it went in the 19th and into this and the 20th century, how it developed? So the first scientific paper in the world of plant disease biology happened in the Gardner's Chronicle, which was in the Royal Horticultural Society magazine in 1865, and the description was about the potato murane, which at that stage people thought it was a disease that came from the cattle. Thereafter, in 1865, the Reverend M.J. Berkeley wrote the next paper saying, no, it was due to a fungus.

And we now know it wasn't quite a fungus. It's something closely related to fungi. But the Irish potato famine was probably the most significant moment in the 19th century in terms of the study of fungal biology associated with disease. Could you develop that? Because people will know about that, that great blight. Yes. The blight's actually caused by, I dare say, a fungus-like creature called phytothra,

and it's still a problem today on tomatoes and obejines and potatoes. But in the 1860s, we had a very extraordinary time in history. Most of the landowners were absentee landlords in London. They were Protestant, and their people who worked the land were Roman Catholics living in Northern Ireland, and they were extremely poor. They were eating between two and a half and six and a half kilos of potatoes a day, and drinking water. If they were wealthy, they had a cow, so they had milk.

So what happened then was that they divided the potatoes that they harvested, and they went mouldy as they stored them from year to year. And they replanted their potatoes. So what you would do is you'd take a tuber, and you put it in a darkened sack, and then the following year you would take the tuber, the potato, and cut it into lots of pieces. So what they did very effectively was to spread a monoculture,

so a genetically uniform stock of susceptible potatoes, throughout Ireland. And then in perhaps, perhaps in the ballast of a boat that travelled from the Isle of White came the potato disease, Phytothra. And this rampaged through the Irish potato fields, leaving in its wake a million dead Irish folk and a million who emigrated to the new world. What was it in that boat from the Isle of Wight specifically, can you tell? What went there and caused such devastation?

This is rumour. No one really knows quite how Fythotthra arrived in Ireland, and this is one of several stories, just simply that there were potato peelings in the boat which had arrived from South America. And of course, South America is the home of the potato. I see. Lynn, how do fungi obtain their nutrients?

So how do they feed? Well, they're not like us. So you and I would eat food, we ingest food, and inside us in our digestive tracts, enzymes break down that food into small molecules which then diffuse into the blood system and spread around our bodies to wherever the energy and other nutrients are needed. Fungi sort of in a way do almost the opposite of that.

They do sort of external digestion. So they don't take food into their bodies directly. They secrete enzymes which break down big molecules outside of their bodies into smaller molecules and then these are absorbed into the fungus. Of course it's a bit of a risky business doing that because other organisms could be around which steal the breakdown products. And this does happen, I dare say, quite frequently with other fungi

and with bacteria that don't have those enzymes that can break down these complicated molecules. And actually quite a lot of other organisms have capitalised on this ability of fungi to break down big molecules. So, for example, termites, the higher termites, they actually farm fungi. Termites and other animals don't have the ability to break down complicated molecules in plants such as lignin and often not cellulose is either the main things that plants are made of. So they culture fungi, they have a garden in their nests, they cultivate the fungi, they clean them up and take any contaminants away, but they bring plant material to the fungus. Fungus, they grows on it, secretes its enzymes, breaks it down.

Of course the fungus can use that material to grow itself, but also some of the termites come along and eat the fungus. So it's a sort of a swap again. The fungi get the food brought by the termites. They break it down into something that the termites can eat. So there are quite a lot of mutualisms like this in South America. Ants do similar things, the aftain ants. In fact, there are loads of these mutualisms which have evolved

because of what fungi can do and how they feed. What, Debbie Johnson, what about the decomposition of material? How does that occur? Well, as Lynn mentioned, it's the production of these enzymes by the heifer, these filaments that grow through soil, that's the critical process. It's all to do with feeding, is it? Absolutely, yes. So the fungi are decomposing stuff, either to get carbon or to get growth-limiting nutrients

like nitrogen and phosphorus. So some of the enzymes that Lynn mentioned are rather specific to those particular forms of nutrients. Some enzymes break down complex forms of carbon like cellulose, one of the main constituents of plant material, other enzymes break down organic phosphorus compounds, which are prevalent in soils, other enzymes break down organic nitrogen. So you end it with a kind of cascade of enzyme reactions going on simultaneously facilitating, the breakdown of that organic matter in order for the fungi to extract the particular nutrients that they require. But it's not just about the chemical warfare. I mean, a key feature of fungi is their ability to physically colonise stuff. So this external digestion process only really

works if you're actually physically attached to the substrate you're interested in. So a key feature of fungi is the ability to grow through organic matter and to penetrate all those tiny crevents. and pores that are found in bits of organic matter in order to facilitate the breakdown of that material. Do the cells of the fungi have any special characteristics, particular characteristics? Yes, I think if you imagine that you're looking at an elongate balloon and the balloon can be anything from a micron,

so 10 to the minus 6, a millionth of a metre, right up to a long tube like you see in a giant tube that you see, not giant, but you can see like licorish bootlaces with dry rot fungi. So those are the filaments which form the hyphy. So the balloon-like structure is the membrane. And what a very particular feature of this fungus is, or a particular fungus, is that it has a cell wall, which confers rigidity to it, so it protects the fungus. And it also allows it to go through different surfaces and also into plants or humans or whatever. And very characteristic of fungi is that they grow by the tip, so they grow by polarised tip growth.

So they grow fast forwards with the tube following them, if you see what I mean, and they're able to colonise all sorts of different environments. But the organelles, that is, the structure within the cell, is very much in common with other mammalian and indeed animal cells. So there are features that are common and also features that are different, particularly the cell wall. We mentioned animals now and that. What are the features that are the same as animals?

So the features that are same are things like the nucleus, so where all the genetic information is held, the way that fungi might make energy. The fact that fungal cells have almost a highway of cytoplasmic contents that are funneled down a cytoskeleton, so it's like thinking you have the motorway, like a neuron, that takes organelles down it to feed the very tip for polarised growth. So many of the organelles within a fungal cell are common to animal cells.

then what's the life is there a life cycle is there a regular life cycle of fungi yes yes yes well obviously there are millions of species of fungi and so there are lots of different life cycles but if we take a mushroom so imagine there's a mushroom there's a mushroom there very useful a mushroom for purposes of illustration absolutely because we can see them in our minds eye quite easily they produce all all of these billions of spores so little tiny spores which are which I suppose are equivalent to the seeds of flowering plants. So these little spores are blown around or maybe taken around by invertebrates or other animals. And a spore might land somewhere.

If it lands in a good environment where conditions are just right and there's a food source, it will germinate. So the fine filaments grow out from the spore, and it branches higgledy-piggledy to start with, starts exuding, secreting its enzymes, breaking down the big molecules and feed in itself and then it can grow bigger and bigger and bigger and bigger.

And it might grow just for a short while or maybe for a long while before it finds a suitable mate. Maybe just a few minutes a spore might have landed right by it which germinates and grows and it can make with that or it might be sometimes perhaps even years. When you say mate, are we talking about any sexuality that we can describe?

Yes, we can. It's quite suitable for our listeners as well. So fungi mate in a rather different way than animals do. The heifi of fungi come together and they simply fuse together.

But that's only successful if they are compatible. Of course we as humans have two sexes, male and female, but fungi have hundreds of sexes very often and they can mate, they can fuse with

many different mycelia of the same species which come close. So maybe a spore has travelled, I don't know, a few hundred yards away from a fungus of the same species and it makes its mycelium and the chances are that they will be compatible so they will mate. They can even mate with mycelium which has developed from spores of their siblings.

Often they can mate very often with about 25% of their very close relatives their siblings sometimes 50%. So they will mate. like this and then they're a little bit different to start with they just have one nucleus in each of their cells but when they've mated they have two and these stay as separate nuclei for a very long time until something triggers them to produce these fruit bodies these mushrooms again so when the conditions are right and the mushrooms start to form then those two nuclei will join together and the genetic material in each of them will

be recombined and then separated again into separate nuclei which go into separate spores and so the cycle continues they will spread away. So that's the main part of the life cycle. But fungi can also reproduce asexually without the need to mate so they can form little spores at the tips of their heifi or sometimes the hyphy these fine filaments that's the main body of the fungus just separate out into very small compartments which then break up. Other life cycles are more complicated. Some of the fungi which Sarah studied is as a plant pathologist have loads and loads of different types of spores

but I think perhaps that's a bit too much to think about here. Is there any way, how are they kept in check? I mean, what you've all been talking about? I sort of wonder why fungi have not been. on the rampage and just taking the whole thing over? Well, in a sense, I suppose in a way they have taken over the planet, but not from a

bad point of view, from a good point of view. They are absolutely everywhere, as Dave has already said. They're intimately connected to plants, helping them all the time. They are breaking down all of the dead stuff that's about. Now, obviously, when they've completely broken down

dead organic matter, there wouldn't be anything left for them to carry on breaking down. So that would call a halt to their activities. So they're governed by and limited by who they can make partnerships with in terms of plants and animals and how much dead stuff there is for them to use. David, can you tell us about these networks and the connections? Just to pick up with that final point quickly, they're also under attack.

So many of these fungi occur in soil where they produce these vast networks of haifi. but those Haifa are susceptible to attack by animals that live in the soil. So things like spring tales, little jumping calumbola. Many of those eat fungi and they do a very good job at it. There's thousands of these little calumbola in soil. So it's not all rosy for the fungi. But yeah, a key feature of fungi is the ability to produce these vast networks. And micraisal fungi in particular.

What would a fungal network be? So it's a mycelium that develops through soil. That's it. That's the simple definition. But some of the fungi, the mycorrhizal fungi, can colonise multiple plants simultaneously. So they develop what's called a common micarizal network. So an individual fungus can simultaneously colonize several individual plants, sometimes of different species. So as soon as you have a physical connection between,

different individual plants, there is the potential for resources to move between those plants via this common microisal network. And in fact, for some species of plants, that's absolutely critical. So many orchids, for example, a hugely diverse family of plants, about 25,000 species worldwide. Many of those plants have actually lost the ability to produce their own carbon. They don't produce any, they don't photosynthesize and they're entirely dependent on carbon moving from a neighbouring green plant via a common microisal network to the orchid to facilitate their growth. So that's like the extreme end of resource movement through these common microisal networks to such an extent that the orchids have evolved away from photosynthesizing on their own.

But these networks can also transfer other molecules. So we now know that they can transfer signaling molecules produced by plants when they're under attack from herbivores like aphids. So it's been found out that when a plant is attacked by an aphid, it can produce signaling molecules that are designed to repel the aphids, but that these molecules can somehow be transferred through these underground fungal networks to neighbouring plants. that aren't yet colonised by the aphid and activate their own defence mechanism before they become under attack. It's bewildering.

What's going on, isn't it? The intensity and the range of it. Saragher, can we take an example of the devastating effect fungi can have? Can you give us one? Yes, so I could divide that into two or three different topics. We could either talk about ecosystems, we could talk about human health or diseases of crops.

So perhaps I'll start with trees. So I think historically many of us were drawn to the study of this subject plant disease biology by the fact that when we were growing up the landscape was changing and it was changing because of a fungus which caused Dutch elm disease and it arrived on a consignment of logs from Ontario in 1974 a very aggressive strain of the fungus and rampaged through the elm trees of Great Britain leaving in its wake up until the late 90s about a million dead elm trees So that's something that's profoundly changed our landscape in the UK.

You see, you emphasised Britain. Did it happen in Holland and Germany? It happened in Europe. It happened devastatingly in Northern America as well. So a huge number of elm trees died. In America they then had a terrible outbreak of a fungus called chestnut blight, which wiped out 1.4 billion chestnut trees. So those two are historical examples. But today, people are very much aware of ash dieback. So this is a disease that probably came from Poland and was,

probably imported into a nursery in Buckinghamshire in about 2012. And today there have been up to today, I think there are just over 1,350 notations or where people have said they've seen the ash dieback fungus. So this is beginning to change the landscape in the UK too. So that's one example. And you said you had two others. So the examples of the impact of fungi on human health is kind of an unseen problem. In the world today, about 100,000 million.

million people are suffering from skin infections. And in fact, the mortality from skin infections when they go invasive, particularly if you are immuno-incompetent, or your immune system is down, means that each year about a million people die from fungal infections. And that means that fungal infections are a hidden peril, causing more deaths than malaria, and in fact more deaths than HIV and tuberculosis added together. And the third one. And the third one is the fact that fungi, as I said earlier, are the most important agents of crop disease. So if you look at the major calorie crops of the world, we know that wheat and maize and potatoes, sorry, wheat and maize and rice and rice cover 40% of global agricultural land. And each of these individual crops suffer from

different perils. So the wheat suffers from rust disease. The potatoes suffer from phytothra, as I talked about earlier. So that's the fourth, not the third. Rice from rice blast disease. and maize from a disease called corn smut. And these individually wipe out a vast amount of crops each year. And if you take just the five major pathogens of plants, we know that they produce or that they compromise our crops so that we are unable to feed between 600 and 4,000 million people, 2,000 calories per day each year. So very significant losses due to fungal disease on crops.

Lyn, this is maybe an odd question. Is there any way that fungi compete with each other? It's not an odd question at all. It's a very good question. Fungi are very, very competitive. Probably competition has been looked at mostly in fungi that rot wood. So if you went to the woodland and soared through a tree trunk that's fallen down or a branch, you'd see lots of lines in there, often dark coloured lines, sometimes bright oranges. And they're not just straight lines. They're sort of demarcate territory. A little bit like how we put fences or walls around our homes and gardens to show which is our area. So fungi do this too

in quite an aggressive way. They completely surround a volume of wood which they can occupy with these defensive materials. So when they've got this territory, they can use the nutrients in that region at their leisure. But of course they're battling all the time against their neighbours who would also like to come in and get that wood from them. And so, Some fungi are better fighters than others. Some of them, when they meet, they were just deadlock. Neither manages to get any of the territory from the other one. Other ones are much more aggressive and can replace completely a fungus.

They do this in different ways. They produce volatile compounds, a bit like the gases in the trench warfare in the First World War. They produce poisonous compounds that dissolve and diffuse through wherever they're growing. to kill their opponents. They produce masses of enzymes which can eat their opponents, and sometimes they're parasitic on them. So there are these great great interactions going along. These battles all the time.

Of course, we can actually use some of these battles for our human benefit. So there's a fungus called trichoderma, which is parasitic and also produces lots of chemicals, which can kill plant pathogens, the sort of things that Sarah has been talking. about a lot. There are other ones which can kill insect pests. So we can gradually begin to manipulate fungi to kill some of the organisms which we find

as pests. And then we come at the end now. But David Johnson, so this is part of the positive uses that fungi have for humans. Yeah. So, I mean, you mentioned at the start, I mean, imagine life without blue cheese, bread, wine and beer. It seems terrible. So that's clearly one use. We like eating fungi and they do great things to enable us to eat very nice food.

So many of the important crop plants, so things like wheat, barley, maize, rice, they're all plants that have evolved to form mycorrhizal fungi and they wouldn't exist without that symbiosis. So I think increasingly we're looking at using fungal diversity to improve the way we grow crops. try and grow them in a more sustainable way, so we're not relying on use of fertilisers and so on. We're not relying on the use of pesticides so much. We're trying to embrace the power of fungi to help grow our crops in a more healthy and sustainable way.

Finally, Asaiga, have we been able to notice the effect of climate changes on fungi? Yes, so in a very large modelling project, we've recently shown that fungi are on the move. And unfortunately, they're on the move in concert with climate change. change. So this is a very... What is on the move mean? So they're moving northwards or polewards at a rate of about seven kilometres per year. So this will have a profound impact not only on the crops that we grow, but the way that we control fungal diseases of crops. So they're marching at the moment. So what effect, can you just tell the listeners, you said they'll have an effect on the crops that we grow? Can you illustrate that?

Yes. So of course the crops that we grow will probably change as well as the climate warms up. And in many regions, becomes also considerably drier. So we'll probably be changing our crops. And as we change our crops, there's a so-called honeymoon period between the planting of the crops and the arrival of new pathogens on these crops. So we've got fungi moving

and crops demography also moving. So we'll see new diseases further north and we'll see diseases as we begin to go, for example, grapevines more prolifically in the northern parts of Europe rather than southern Europe. And we'll probably see the pathogens, on the march with the crops.

Well, we'll leave the pathogens on the march. Thank you very much. Thank you very much, Goet. Lynn Boddy and David Johnson. Next week we'll be discussing Roslyn Franklin, who played a vital role in discovering the structure of DNA. Thank you for listening. And the In Our Time podcast gets some extra time now

with a few minutes of bonus material from Melvin and his guests. So what did we miss out? What were you bursting to say that you didn't say? Oh, well, I think that there's lots of things. really I think one thing is that we use fungi or fungal products as humans in very important ways in addition to what Dave has mentioned earlier. For example, lots of medications, obviously penicillin, an antibiotic is one of the things which springs firstly to mind. But fungi also make other drugs which we use. So ephidrine, which is used to treat asthma, ergot alkaloids, which are used as vasoconstrictors.

to treat migraines, induce uterus contractions. Statins we discovered from fungi in the first place to treat cholesterol to lower cholesterol. They're also important in the production of some steroids. Citric acid acid, I think nearly all soft drinks, has citric acid as an acidity regulator. That is made commercially by fungi in vast vats and other things like a scorbic acid,

as well, alcohols and ethanol, enzymes such as proteases for softening meat, tenderising meat, pectinases for breaking down plant cell walls, which releases more juice when you're making fruit juice, various vitamins such as vitamin B, beta carotene, all sorts of things, plant growth factors for stimulating the rooting compounds, you know, plant hormones, there's a vast amount of products from fungi. we might have just emphasized too much the fact that fungi are our foes. In fact, they're also our friends as well. But borrowing an idea from Neil Gow in Aberdeen, I think we should think about fungi as citizens of modern society because they're ethnically diverse and huge in number.

They're important for recycling. They're important as scholars and teachers, which is something that we didn't really dwell upon very much, because in fact many of the things that we've learned from fungi, work by Sir Paul Nurse, have told us about the cell cycle, pivotal to cell biology. They do all sorts of other things in the environment that are useful for us, that we've talked a bit about, but they also, not only scholars and teachers, but they are problems, so they make our feet smell, they make our houses rot and they destroy our crops. So, but we must emphasize that there are very positive things, such as the drugs and the enzymes that come from fungi, without which life would be very much sadder without the wine and the cheese.

You were a bit of kin on the wine and the cheese, David. Indeed, yeah. I live a good blue cheese, which is a penicillin like fungus that produces that type of cheese. So it's not just producing the antimicrobial stuff, it's producing a delicious product. The other thing to emphasise, I think it's just the vast abundance of these fungi in soils. A teaspoon of soil typically contains something like 10 to 100 metres of haifi. It's a vast amount. And I think we need to understand that.

You know, when we're thinking about our ecosystems, particularly our forests, there's just a vast underground world supporting that ecosystem, which is so important for life on Earth, in regulating our climate, in producing food, fuel and fibre. It's really dependent on these fundamentals. Yeah, so you've just talked about these huge long areas, long distances in areas that the heifer cover. But actually the largest organisms on the planet are fungi.

We often think that it's the blue whale or something like that. But the honey fungi, the armillarias form networks through forests. And some of the largest ones, we have large ones in the UK, but probably the largest ones in the huge forests of North America, where from one side of a network to the other could be over three miles, so they can be absolutely huge. We can't see this, obviously, because they're below ground, doing whatever it is, they're doing, decomposing dead stuff,

and in some cases using living trees and things, but they can be quite huge. What benefits do they get by being so big? Well, I think the benefits they get from being networks, rather than necessarily from their size. Dave mentioned networks earlier. It's not only the microisal fungi that form networks, many fungi which grow into soil form networks

and being a network you can send stuff from one place to another so if a fungus is growing into a region which is desert like in terms of maybe not enough moisture not enough nutrients through the network a fungus can feed that region with food from elsewhere

also networks if you break a network like for example if you've got a road network and you close a road there are other ways that traffic can go can go, and that's also the same in these fungal networks. So these huge networks have access to nutrients all over the place. And in fact, some transport networks are remarkably similar in structure to fungal networks. It's been some very nice work comparing the underground networks of the major cities with fungal networks.

So, yeah, they like an insurance policy. You know, they provide resilience if a host plant dies over there, while the fungus might have another source of energy over here, for example. And they can also help in this competition, so they can direct resources to these battlegrounds, you know, where the energy is most needed. So they're hugely important. Hello, I'm Jenny Murray.

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