If you’ve ever sprinkled nutritional yeast on your eggs or popcorn, chances are you never gave much thought to what it really is. Sure, it tastes great — that savory, almost cheesy punch is beloved by keto and vegan fans alike. But beneath that flaky yellow powder is something truly weird.

Yeast isn’t a plant. It isn’t bacteria. It isn’t remotely animal. It’s something stranger — it’s a fungus. And not just any fungus, but one that, when alive, behaves in a way few other fungi do.

A Living, Breathing (Well… Excreting) Fungus

Yeast is part of the vast and bizarre fungi kingdom. Unlike mushrooms (which grow fruiting bodies and spread spores), yeast is single-celled and lives much like bacteria — feeding, multiplying, and most notably, excreting waste products as it consumes sugars.

That’s right: When yeast is alive (think baker’s yeast in your bread dough or brewer’s yeast in your beer), it actually eats sugars and excretes gases (carbon dioxide) and alcohol.

• The CO₂ makes bread rise.
• The alcohol makes beer… well, beer.

No other common kitchen fungi work like this. You don’t toss shiitake mushrooms into dough and watch them make bubbles. Yeast is unique in how it lives and contributes through fermentation, a process more akin to bacterial metabolism than mushroom growth.

Same Critter, Different Job

So what happens when yeast is killed and no longer active? Enter nutritional yeast.

This is the same Saccharomyces cerevisiae species, but it has been grown, harvested, and then heat-deactivated — meaning it’s dead. No bubbling, no fermenting, no more life. Just a pile of nutrient-rich cells and savory compounds.

That dead yeast brings serious nutrition:

• High levels of B-vitamins (often fortified with B12 for vegans).
• A complete protein profile.
• Naturally savory glutamates that give it its umami kick.

In this state, yeast becomes a flavor enhancer and dietary supplement, but is no longer alive.

Fungi: Closer to Animals Than Plants

Here’s where it gets even wilder.
Most people assume fungi are closer to plants because, well, mushrooms grow in the woods and don’t move. But biologically, fungi are much closer to animals than to plants. In evolutionary terms, fungi and animals share a more recent common ancestor than either does with plants.

In fact, fungi and animals both:

• Consume organic material (they don’t photosynthesize).
• Store energy as glycogen.
• Have chitin in their cell walls (animals have chitin in shells and exoskeletons; plants use cellulose).

Yeast carries all of that genetic baggage right down to its single cell.

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How Yeast Reproduces: The Budding Bonus

Here’s another mind-blower: when yeast is alive, it doesn’t just hang around. It reproduces — and not like bacteria or plants.

Instead of splitting in half like bacteria (binary fission), yeast cells use a process called budding:

• A small bump (bud) forms on the parent yeast cell.
• The cell’s nucleus divides, and one copy moves into the bud.
• The bud grows, matures, and eventually pinches off to become its own yeast cell.

This is mitosis in action — much like how animal cells divide — but with a fungal twist. Yeast literally grows little versions of itself right on its side, like tiny balloons eventually floating off into independence.

The Little Fungus That Could (And Does)

Yeast plays roles no other fungus does in everyday life:

• Makes your bread rise.
• Ferments your beer and wine.
• Enhances your meals as nutritional yeast.
• And when alive, grows and reproduces like a microscopic creature right out of science fiction.

All from a tiny, humble critter that was alive… and now isn’t, but still working for you.

So next time you sprinkle nutritional yeast on your plate, know this:
→ You’re eating the same organism that brings bread to life and powers beer fermentation.
→ You’re tasting a fungus that — biologically speaking — is more like an animal than a plant.
→ And you’re partaking in something that, when alive, grows new versions of itself in the coolest way possible.

Yeast — nature’s tiny shapeshifter. Not plant, not animal, not bacteria. Just… yeast.

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Dave Soulia | FYIVT

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