Fascinating Bacillus cereus#
Sep 05, 2025 - Welcome to “Fascinating Shit!” with Peter. This week, I’ll tell you about Bacillus cereus.
From the word Bacillus, you can tell this is a bacterium, which we might also call a microbe.
The ugly kind.
The spores of B. cereus survive high temperatures.
And once cooled down to room temperature, they start to germinate into the real germs.
Latin prefix Cere- means waxy, describing the waxy colonies the bacterium forms.
And waxy these colonies are: opaque, whitish to cream, round, 2-7 mm after 24 hours of growth, odorless, and tasteless.
The bacteria are widespread in soil, and they send the spores up to the plants’ surface, where they sit still waiting for better conditions.
And the best conditions for the spores are moist food starch, the one you find in rice, pasta, and potatoes.
This germ produces Cereulide, which, literally translated, means “cyclic peptide from Bacillus cereus”, also known as emetic toxin. This toxin has a few interesting properties:
Extremely heat-stable, survives boiling, frying, and reheating.
Acid-stable, survives stomach acid.
Lipophilic, which helps it pass into cells and disrupt mitochondrial function. This triggers nausea and vomiting within a few hours after ingestion.
So what does it mean in practice? If you get a bag of rice, you can be 100% sure it has cereus spores from the soil it grew on. When you boil it, bacteria die, but spores survive. If left unrefrigerated, spores find themselves in a warm, moist, starchy bowl of rice and start to grow bacteria. Again, this is not a chance or bad food handling; this happens, period. Grown bacteria colonies look almost like rice. And they start producing Cereulide.
So, the next day, you reheat your rice, you can even boil it, it doesn’t matter. The toxin stays. It doesn’t affect looks, smell, or taste. But one hour later, you get nausea and start to vomit. Some people refer to this as the classic “fried rice syndrome.”
So, next time you cook rice, don’t let it sit for too long, cool it down and put it in the fridge. No matter what you do, it will have some bacteria and toxins. But not enough to cause a severe reaction, if you do it right.