How fungi shape our world
This episode of The Naked Scientists was brought to you in partnership with the health foundation Wellcome. This week, the first in a two-part series on the hidden world of fungi. What we do - and don’t - know about them, and how the fungal landscape is set to shift as our climate changes.
In this episode
What are fungi?
Sumi Robson, Wellcome
Fungi are older than the dinosaurs, stranger than science fiction, and more essential to life on Earth than most of us realise. They first emerged over a billion years ago in the planet’s oceans and, since then, they’ve taken over. From the depths of hot springs to the crust of salty lakes, fungi thrive in the most extreme environments. Their spores hitch rides on every breeze, and their hidden networks outweigh all the animals on Earth. Yet despite their power and presence, fungi are still one of the most mysterious kingdoms of life, and studied far less than our plants and animals. With that in mind, we are embarking on a two-part series, brought to you in partnership with the health foundation Wellcome, to take you on a journey into the strange, spectacular, and often overlooked world of fungi. To begin, here’s Sumi Robson who is Wellcome’s Senior Research Manager…
Sumi – Fungi are a kingdom, the same way that animals are a kingdom or plants are a kingdom, and if you think of everything that encompasses the animal kingdom—everything from insects to a blue whale—or in the plant kingdom, we're talking about mosses or herbs to the big oak tree, it's the same for fungi. We've got teeny tiny single-celled organisms like yeast—we need these to make bread—or yeast that ferments sugars…
Chris – Go on, say beer!
Sumi – Yeah! And in the same way, with fungi, we get these large multicellular fungi as well. Actually, we now think the largest organism in the world is not the blue whale—it's a fungus. And that's found in Oregon, in one of the national parks, and it sprawls across acres and acres and weighs tonnes and tonnes.
Chris – Goodness. If one winds the clock back, then where do fungi come from? Where, in the tree of life on Earth going back four and a half billion years, do fungi fit into the picture?
Sumi – So we think they, similar to plants, started their life in the oceans. And around the time that plants moved from the oceans onto land, fungi did the same. Actually, we now think that plants wouldn't have been able to make the transition from the sea onto land without fungi, because they didn't have roots in the sea—they didn't have a way of getting into the soil and accessing all the water and nutrients they need. So what we think is that fungi and plants formed a sort of symbiotic, mutual relationship that allowed plants to come onto land and colonise the Earth—which was a huge change for the planet. If you think of what the atmosphere was like back then, really full of lots and lots of carbon dioxide, what plants did was take in that carbon dioxide, photosynthesise it into sugar, and release oxygen—which is what allowed us to evolve. And all of that wouldn't have been possible without the fungus that the plant paired with.
Chris – That relationship, that very tight-knit relationship between a fungus in the ground and a plant growing in the ground—that persists to this day though, doesn't it? Because fungi and plants have a really special relationship—a bit like the UK and American one we used to have—that means one complements the other?
Sumi – Yeah, absolutely. Something like 90 percent of plants on Earth have this relationship, and we hope that it never breaks down like our relationship with the US! Because if it does, I think the plants would really suffer. And that's something we're starting to really recognise in terms of more sustainable agriculture—so if you can get the right fungal species with the right crops, we can really enhance crop growth and reduce the need for pesticides and fungicides, which none of us really want on any of our foods.
Chris – Because the fungi can do things the plants can't, and vice versa. So the plants—they're making sugar, which they trade for things the fungus can make or go and grab using those very extensive soil networks you were talking about.
Sumi – Yeah, absolutely. So plants are great at photosynthesising—they get carbon from carbon dioxide and make sugars, which the fungi can't actually make on their own, the same way we can't; we eat food. But what fungi are great at doing is decomposing—so they produce lots of enzymes out into the soil, they can break down rock and stone, they can even break down plastics. What that does is release lots of minerals and nutrients—things that the plant can't get in any other way, things like phosphorus and nitrogen—and that really helps the plant. So they live in this kind of mutual relationship, which, to be fair, isn't always static. Changes in the environment mean that sometimes the fungi benefit more, and then sometimes the plant benefits more, but they kind of always settle back into a balance.
Chris – Do we, as animals, have a similarly close relationship with fungi that the plants do?
Sumi – Similar, but different. Fungi are more similar to us than they are to plants, at the cellular
level. If we think of the molecules and the proteins, there's more similarity—which really has its advantages. If we're trying to understand something about one of our proteins, it's quite tricky to do experiments or to meddle with ourselves, but we can take a fungus cell, look at that similar protein, and understand how it's working in the fungus, then translate that to humans.
Chris – Earlier in this conversation you mentioned synthetic biology—in the sense that I interrupted you and said 'beer'! I was just very fond—I was very thirsty—and I was thinking it'd be quite nice to have a cold one, which we depend on them entirely for. But they also make massive contributions to the pharmaceutical industry and biotechnology in other ways. We can use them to make other stuff, can't we? So where would we be without fungi in that respect?
Sumi – I think medicines are probably the really key one where fungi have contributed to date. Because fungi live in an ecosystem, they're constantly at battle with other organisms—other bacteria and viruses—and they produce things in that battle. Penicillin, a classic antibiotic we've all heard of, was produced by a fungus trying to out-compete bacteria in its environment. But also things like cyclosporine, which is used for transplant patients—all really key drugs that are produced by fungi. So they've really contributed to human medicine over the years. But I think, going forward, the potential for fungi is amazing—partly because of their similarities to humans, partly because of their capacity to store carbon and to degrade other matter. I think in carbon capture, to mitigate against climate change, and for more sustainable agriculture—where they're able to form those mutual relationships we talked about—really working to enhance those could help ensure food security for the population, especially where climate change is affecting that more and more.
Chris – So why does the Wellcome Trust regard this as a priority now? Why do you have the job that you do—leading this kind of aspect of what the Trust is doing? Why is it now regarded as a priority?
Sumi – For me, I think there are three main things that make this the right time to be thinking a bit more about fungi. Firstly, it's to do with climate change—we are seeing fungi adapt at an amazing rate to the changing climate, and that's something we need to get on top of. Secondly, we don't really know that much about all the fungi that are out there. We think there are something like four million species, but we've only really described and found about 10 percent of them. So there's so much we don't know. We've only found about 10 percent, and we haven't really studied them that much. So compared to what we know about bacteria and viruses, we don’t know as much about fungi—and yet they're so similar to us.
09:07 - How diverse is the fungal kingdom?
How diverse is the fungal kingdom?
Lee Davies, Kew Gardens
To unlock the secrets of fungi, we need to uncover how many of them are out there, and how their sometimes strange and powerful biologies and chemistries actually work. With that in mind, we sent Will Tingle to the world famous Kew Gardens in London…
Will - As Sumi Robson just pointed out, there are potentially as many as four million species of fungi in the world, of which we've only described about 10%. That means there's a lot of catching up to do when it comes to categorising and understanding this particular kingdom of the tree of life. That's why I've come down to the world-famous Kew Gardens and its fungarium to find out what that work entails.
Lee - My name is Lee Davis. I'm the Collections Manager for the Fungarium, which means I'm a kind of glorified librarian of mushrooms.
Will - It's delightful to be at Kew Gardens’ fungarium—such an illustrious building. And I guess for the audience at home, I'd describe it as the end of that one Indiana Jones film—the warehouse, but full of mushrooms. Is the Ark of the Covenant here anywhere?
Lee - It is, but I can't tell you where it is, because we keep that for ourselves.
Will - That's fair enough. We should probably stick to fungi then in that case. I'm reading that there are 1.2 million samples of fungi in this building—is that true?
Lee - We have 1.1 million specimens. As for species, we're not totally sure—it's probably something like 60,000 to 70,000, maybe up to 100,000.
Will - Where are they found? Is there a particular biome or environment that they're happiest in, or is it literally everywhere?
Lee - Fungi originated in the oceans, along with everything else, so there’s a whole gamut of species in the oceans that we know about, and probably hundreds of times as many again that we haven’t discovered. The vast majority of the fungi that we know and have described scientifically all come from terrestrial environments. But you can find new species in the weirdest of places. I think it was two or three years ago someone described a new species of fungus found on an oil painting, underneath someone’s fingernail, and on a plastic child's backpack, I think it was. So they are everywhere and anywhere at any given time. Some of my favourites are the entomopathogenic fungi—the ones that parasitise and do horrible, horrible things to arthropods. The classic example is Cordyceps fungi—the ones that infect them, manipulate their behaviour, and eat all the insides out of their hosts before bursting out of their heads. I really like those. But right next to us—we’re next to the Amanitas, and I think Amanita muscaria is one of my favourites. That’s the red one with the white dots that everyone knows. It’s fun for all sorts of reasons. Ecologically, it’s a mycorrhizal fungus, so it has this really unusual and interesting relationship with trees. It has a lot of places in human culture—from fairy tales (it’s the one we all know from video games), but it’s also a super hallucinogenic fungus. Humans have been eating it for thousands of years for that reason. Some of the other Amanitas are also horribly toxic—will kill you very slowly and painfully. But the toxins are really interesting from a pharmaceutical point of view, because if we can apply them to cancer cells, they kill cancer cells preferentially. So the Amanitas are really interesting for lots of human-interest stories.
Will - I was fortunate enough a few years ago to be up in Svalbard, and I caught a glimpse of the Global Seed Vault—which is quite secretive but a very interesting storage facility for so many plant specimens, in case something goes really wrong on the rest of the planet. Can that idea be applied here, or is this more research-oriented?
Lee - So the collection we have here in the fungarium—this is dead and dried mushrooms. The idea isn't about preserving them to grow again; it's about having a kind of snapshot, a microcosm of the world's fungal diversity so we can study it for taxonomy and ecology. Then we can start to explore it in terms of genomes, for novel enzymes and drugs we might want to use. Kew does have a kind of fungal seed bank. So down at Wakehurst, on the Kew site, we have the Millennium Seed Bank, which is a non-agricultural version of the Svalbard Seed Bank. I think the idea is to try and have seeds from every plant on Earth as a backup. And it turns out that probably all of those seeds have fungus in them—non-pathogenically. It’s just living inside them, not causing any disease, just doing its own business. So we kind of do have our own Svalbard—but it’s in Wakehurst. Pretty equivalent, I would say. In terms of scenery, a bit warmer—and no polar bears. For now.
Will - What kind of work, then, is going on with these?
Lee - The vast majority of what we do here with this collection is taxonomy. So, what fungi are out there in the world, how are they related to one another, and just understanding fungal diversity across the world.
Will - Have there been any interesting discoveries that have changed our perception of fungi, originating here?
Lee - Yes. A good example of this—up until about 20 years ago, all fungal taxonomy was based on morphology: what does it look like, what do its spores look like under a microscope, what do the sex cells look like. It’s physically derived information. Turns out it’s horribly inadequate.
A great example that comes from here—one of our former heads of mycology bought some porcini mushrooms in the supermarket (dried Boletus edulis), brought 13 pieces here into the lab, and sequenced all 13. Turns out none of them were actually Boletus edulis. There were three different species in there, all of them new to science. So the diversity is much higher, and it’s very, very easy to split an individual species into maybe half a dozen or more based on DNA. And we can do that here with the collection. It’s relatively easy to find a new species to science hidden in these boxes—really easily.
Will - Once you start to do DNA analysis, do you have any particular favourites in this collection that you'd be willing to show me?
Lee - Okay, so—this is Bev. Bev was a tarantula. So this is just the normal tarantula. This is a Megale bird-eating spider that’s been parasitised by Cordyceps caloceroides. That’s one of these Cordyceps-type fungi. It’s invaded her body, probably manipulated her behaviour, and then finally killed her and eaten all of her guts before these two big long orange fruiting bodies popped out of her leg joints.
Will - It almost looks like a nice exoskeleton of a tarantula has gone for a swing on a couple of vines.
Lee - Yeah, it does look like she’s wearing streamers. They're really pretty.
Will - So am I right in thinking then that these long tendrils erupt, and the spores come out of them and spread further to the next unlucky arachnid?
Lee - That’s exactly it. On these fruiting bodies—mushroomy-type things—they’re just long strands rather than a mushroom, but they’re about six to eight inches long. The top two or three inches will be fertile, so they'll be producing spores. And because they’re lifted above the leaf litter by their height, the spores will drift on the wind. They’ll either land on another spider or land in the leaf litter and wait for a spider to tread on them and get picked up.
Will - These are also very much in vogue at the moment, thanks to a very popular TV show. I'm sure you're sick to death of discussing it. But for the listeners at home—the realistic chance of that happening to us is probably quite low?
Lee - It’s low—but not zero. The things in our defence are: we’re too hot—mammalian body temperature is too warm for these fungi; they don’t like it. But natural selection and climate change are going to push their tolerance. We also have quite a good immune system. Also, these Cordyceps-type fungi that manipulate behaviour and turn insects into zombies—they've been doing this for, like, 60-odd million years. We know that there are ants in amber with Cordyceps on them. So they’re not really out to get us—they already have their favourite food. That’s what they’re triggered by when it comes to germination and development. They’re not interested in humans—yet. But climate change, natural selection—who knows what'll happen as we get exposed to these over the coming decades. Never say never.
17:44 - Why fungi are the backbone of the ecosystem
Why fungi are the backbone of the ecosystem
Lynne Boddy, Cardiff University
Fungi have been quietly thriving for millions of years, intricately woven into the fabric of life on Earth. They underpin ecosystems, support food webs, and drive the nutrient cycles that allow life to flourish. They have often gone unnoticed, until recently. As Sumi said at the start of the show,. Fungi first evolved in the oceans, and struck up an extremely beneficial relationship with plants that allowed the latter to colonise the land by harnessing their newly evolved roots to take in nutrients from the soil. So, how has that relationship evolved with both plants and animals, and what pivotal roles do fungi play in keeping our delicate planet ticking over? Lynne Boddy is a microbial ecologist at Cardiff University…
Lynne - Fungi have evolved hand-in-hand with plants. A huge range of different mycorrhizal associations have evolved. Also, as more complicated plant life forms developed with more complex building blocks, fungi evolved the enzymes required to break them down as decomposers.
So there's this continuous hand-in-hand evolution. Fungi also interact with animals and, actually, they're very important for many animals. They're an important food source – and I'm not just referring to their fruit bodies, but also their mycelium.
Many soil invertebrates feed on fungal mycelium because it's very nutritious. It's high in phosphorus and nitrogen, which are hard for organisms to obtain. Of course, many invertebrates don't produce the enzymes they need to break down complex substances.
So many soil invertebrates feed on fungal hyphae either directly or indirectly by eating decaying material, which contains fungi that are doing the decomposing. But also, some fungi and invertebrates have evolved successful mutualisms somewhat similar, I suppose, to the mycorrhizal relationship in terms of obtaining food. One example would be termites.
The higher termites in the group called the Macrotermitidae farm fungi in their nests. So when they establish a new nest, they have to go away and find an appropriate fungus, which they inoculate into their nests. And they bring food to the fungus.
The fungus can break it down because the termites don't have the enzymes for breaking it down. They don't have enzymes to break down complex lignocellulose, but the fungi do. And then the fungi produce various structures on their hyphae, which the termites eat.
And so it's a win-win situation. The fungi are being fed, and the termites are being fed by the fungus. And there are loads of these mutualistic relationships.
It's not just invertebrates, in fact. There are important relationships between fungi and many animals, including mammals. We have fungi in our guts. And animals such as ruminants, like cows, depend on fungi too – and other microbes in their rumen – for breaking down the grass that they eat.
Chris - The picture you've painted is one of fungi playing this enormously important, central role in biology – helping to support the growth, but also the end of life, of a range of different species and systems. How vulnerable are fungi, though, to a change in the environment? Because one of the things that's changing very fast is the climate.
And we anticipate big shifts in that direction in very short timescales – far shorter than evolution can normally keep up with. So are we worried about that? As a biologist, are you concerned about what that may do and whether fungi can keep up?
Lynne - Climate change is certainly affecting fungi hugely – in terms of their distribution, their activity, the timing of events in their life cycles. These are all changing. And we can see this, actually, when we look at large historical databases of records of when and where fungi were found fruiting.
A really obvious example is the autumn fruiting season, which is changing. As you know, in temperate parts of the world, most fungi tend to fruit in the autumn – some fruit in the spring as well. But what we’ve found is that, on average, the autumn fruiting season is now starting earlier and lasting much longer.
So before about 1980 in southern England, the average fruiting season was about 33 days. And it's more than double that now. You might think, well, you know, I'm not particularly interested in fungal fruit bodies – but I think this is really telling us something about the fungi.
Not all fungi are behaving the same. Some species behave differently, obviously. So, for example, as a whole, the decomposers are tending to start fruiting earlier.
But the mycorrhizal fungi that associate with trees are tending to start fruiting later in the year. And this is probably because trees – and indeed other plants – carry on photosynthesising for much longer than they used to. So the triggers for fruiting are coming later in the year than they used to.
We’ve also found that the mycorrhizal fungi associated with conifer trees in England tend not to have changed very much, but those associated with deciduous trees have changed their fruiting time to later in the year. So climate change and its effects on fungi seem to be affecting different ecosystems differently.
Chris - And what might be the consequences of that, Lynne? Because does that mean that even though one thing's changed, because another has, there must be knock-on consequences? There’s going to be a sort of domino effect through the ecosystem because of this, presumably.
Lynne - Actually, quite a good example might be another effect of climate change on fruiting. And that is that with many of the decomposer fungi – especially the wood decay fungi – a lot of them are now starting to fruit in the spring, which they never did before. And what that is telling us, I think, is that those fungi are now active in the winter, when they probably weren’t before.
At least, they’re more active in the winter – breaking down dead material to obtain nutrients, which allows them to make fruit bodies in the spring. So I think the implication is that there is more decay happening. Decay is happening faster.
That’s OK, provided that there’s a balance in the system – in other words, that plants are photosynthesising at a greater rate to make up for this more rapid decomposition of the dead material. Now, if that’s not happening, the system will no longer remain balanced.
So if we have more decay than new material produced by photosynthesis, we will find that there’s more carbon dioxide being emitted into the atmosphere. And, of course, that will exacerbate the problem we already have of global warming and global climate change.
25:04 - Will climate change cause more fungal disease outbreaks?
Will climate change cause more fungal disease outbreaks?
Norman van Rhijn, University of Manchester
As the COVID-19 pandemic demonstrated, any disruption to the delicate balance of nature has a ripple effect, inevitably reaching us. While common fungal infections like ringworm and yeast can be managed, more dangerous and virulent strains lurk in the shadows. In 2020 alone, an estimated 1.7 million people died from fungal infections. It’s a reminder of the potential threat fungi pose when left unchecked. With climate change accelerating and reshaping our planet, the big question remains: will we see more deadly fungal diseases emerge, propelled by the changing environment? The University of Manchester’s Norman van Rhijn explains more…
Norman - Fungi are a vast kingdom of different species, so they really are all around us. They have their own niches, their little homes where they like to live, but obviously, when the world is changing, some places become hotter, some places become wetter or drier, and the fungi will adapt to that accordingly. So they will move into new spaces, they will evolve, and that's what we're likely to see in the future.
Chris - What are you most worried about in that respect? When one considers these sorts of changes in the future, there must be some things that you use as your poster child for this happening, but also things that you say, this is a really big concern if this happens.
Norman - Well, we do a bit of research on a yeast called Candida auris. We didn't know it before 2009, but since then it has spread across the world and caused these life-threatening infections and outbreaks that we've really not seen before. And we think this is the first example of a fungal species that came to be because of climate change.
It's a new species; it's evolved with climate change and is now causing these infections. So my fear is that something like this will happen again, or even worse, we get a fungus that can infect everyone. Luckily, so far, we tend not to see that.
So Candida auris infects people who are already in intensive care, but they are really hard to treat. So yes, a lot of worries over the next 50 years or so.
Chris - What's the mechanism then? Because you're saying that is really the first documented example of a climate change-driven emergence. Why and how?
Norman - We have only a few published cases of where this yeast can be found in the environment, but we've not really pinpointed it as a field. So that's what we're trying to do. And then the next thing we're trying to understand is what traits it has evolved, and why it can infect.
There are some indications. It forms these great biofilms that stick to surfaces and can stay there for long periods of time. It can withstand high temperatures — higher than body temperature.
It can cope with stress really well. It grows rapidly. So these are the things we're looking at.
But so far, we've not pinpointed one particular niche or factor that is driving these infections.
Chris - Have you pinpointed any areas of the world that are likely to be particularly challenged or challenging in this respect? Because we know there are going to be some areas where climate change impacts are greatest, either because the human impact is greatest, the environmental impact is greatest, or both. So are there some hotspots that are likely, therefore, to translate into big changes in what fungi do?
Norman - I think, unfortunately, every part of the world is going to be affected in a different way. And there will be fungi that take that opportunity. I think we already see that fungal infections are a really big problem on the African continent, where we have lots of people still with tuberculosis or HIV, and these are risk factors for severe fungal infections.
And because the antifungals that work relatively well are expensive or not even available in those countries, that is where we see the highest rates of death. So I think if I have to focus on one particular area, it's going to be that. But we're going to get other problems in Europe and North America as we see more people going into intensive care or being severely immunocompromised.
These fungi are great opportunists — if they see a way to consume you as organic matter, they will.
Chris - Pleasant thought. And in terms of the threat that this poses to the environment — because when you've got an infection that's in humans, it's easier to control, because you can control what humans do and you can medicate humans and so on. But when it's an environmental threat and it's got the whole of nature to play with, it's much, much harder, presumably.
Norman - It really is. So thinking about things that infect animals — it's really difficult to treat. There was a fungal infection which was rampant across amphibians, and we saw rapid decline in these animals.
There's an example of outbreaks among these parrots — kakapo species that are already close to extinction — and it wiped out about 10% of the entire population. But also, if we think about plants and crops — massive crop loss — and trying to rein in fungal infections is incredibly difficult. And that is why our farmers are having to use tonnes and tonnes of fungicides each year to save their crops.
Chris - But are they paradoxically accelerating the problem by doing that? So as we effectively pour more petrol on the fire to control it, we're actually driving the evolution of these fungi and possibly intensifying things?
Norman - Partially, but there is a group of fungi that are the main drivers of plant infections, and only a very limited group are able to cause both plant and human infections. So they're still a relatively separate problem. But there are some examples where we have these cross-kingdom fungal species, and actually what we already see is that they are exposed to these chemicals in fields — and that's exactly where they start to evolve resistance to the antifungals we use in the clinic.
So we've got this dual problem of trying to fight both nature and evolution.
Chris - We've dwelled quite heavily on the bad news. Hopefully you've got some good news for us in terms of what we might be able to do about this in order to swerve around some of these things that you say are the rocks in the path ahead.
Norman - Luckily, it always starts with awareness. And I think if we compare where the field is now to 20 years ago, there's a lot more awareness and cross-talk between these fields of research. So we now see that clinicians are starting to speak to farmers and to policymakers so we can actually start doing something about it.
On top of that, we've got some great novel molecules that are hopefully going to come out within the next few years in agriculture, and also to treat human infections. So I've got great hope that there will be something out there that we can use to treat these infections.
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