What are fungi?

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.