Year of Soils column by Annemieke van der Wal

I’m sure we’ve all seen what fungi look like. From the fuzzy grey mold on strawberries that have gone bad to those colonies of small green patches on stale bread or the mushrooms outside in the forest that thrive on decaying wood.

But while they’re often visible to the naked eye, fungi are in fact micro-organisms just like bacteria. Normally, you’d need a microscope to look at micro-organisms because they’re so tiny. How come, then, that you don’t need one for fungi?

Fungi consist of microscopically thin filaments known as ‘hyphae’. These hyphae will mat and branch to form colonies or mushrooms that can easily grow to several centimetres.  In fact, some fungi may form threads of up to hundreds or even thousands of kilometres.

A well-known example is the honey mushroom. Its hyphae  can easily cover 15 hectares of forest soil. Some honey mushrooms are estimated to be 1500 years old or more. They’re known as the largest living organism on earth.

So why do fungi form these filaments? Because they’re clever! By forming long threads, they can grow towards their food. And they can transport the food along the filaments to the parts of the network where it’s needed the most.  Fungi are also great recyclers. Any part of the network that is no longer needed is broken down and digested.

Not all fungi form filaments. There are also single-cell fungi such as yeasts, which can turn sugar into alcohol and are used to make wine, beer and bread.

But one the most intriguing qualities of some fungi is that they’re the only organisms that can break down the second most abundant source of carbon on the planet: lignin. Most trees need lignin to support their tissues or else they would collapse. Without fungi, we’d all be up to our  eyeballs in plant remains. If there were any life possible on earth at all without them, that is!

So there are plenty of reasons to feel something of awe for these organisms that are at once small and great.