Are fungi single-celled or multicellular?

This question comes from school biology, but people really do type it a lot — often alongside the names of specific mushrooms: “is a slippery jack single-celled or multicellular”, “is a button mushroom…”. The short answer: most fungi are multicellular, but there's one important exception — yeasts.

Multicellular: almost all the mushrooms you know

The mushroom you cut in the forest is only the fruiting body of a large multicellular organism. Most of it hides in the soil or wood — that's the mycelium (the fungal network), a tangle of fine threads.

• These threads are called hyphae.
• Hyphae are made of many cells, often divided by cross-walls (septa).
• The fruiting body — cap and stem — is also built from tightly interwoven hyphae.

So porcini, slippery jacks, button mushrooms, honey fungus — they're all multicellular. We've covered how long mycelium lives in a separate article.

The single-celled exception: yeasts

The main exception is yeasts. They're true fungi, but they live as separate single cells that reproduce by budding. Yeasts are what make dough rise and ferment grape juice into wine.

So when someone asks “are fungi single-celled or multicellular”, the most accurate answer is: fungi can be both, but the vast majority of the species we forage are multicellular, and the single-celled ones are mainly yeasts.

Which kingdom fungi belong to

And one more question that often comes up: fungi are neither plants nor animals, but a separate kingdom of living things (Fungi). They don't photosynthesize like plants; they feed on ready-made organic matter like animals do — which is why they were set apart.

Sources

• “Identification Guide to the Fungi of Ukraine” (Kyiv, Naukova Dumka publishing house).
• Fungus, Hypha, Yeast on Wikipedia.