Why the bacteria in your leftover rice is a master of survival

Nature · Published 3 October 2026 Swipe more like this →

In short: Bacillus cereus is a resilient, soil-dwelling bacterium that thrives in environments where others perish. While often associated with food poisoning—specifically from improperly stored rice—this organism is also a complex biological machine capable of forming protective spores, building biofilms, and even producing potential biodegradable plastic substitutes.

Bacillus cereus is a Gram-positive, rod-shaped bacterium that exists as a facultative anaerobe, meaning it can survive with or without oxygen. Its name, derived from the Latin for 'waxy,' describes the appearance of its colonies on blood agar. These bacteria are ubiquitous in soil, but they are also notorious in the food industry for their ability to form spores and biofilms. These structures allow them to withstand conditions that would kill most other microbes, including standard cooking temperatures. While vegetative cells are destroyed by boiling, their heat-resistant spores can survive, germinate, and multiply if food is left in the 'danger zone' between 4 °C and 60 °C.

The bacterium causes two distinct types of foodborne illness. The diarrheal syndrome is linked to enterotoxins produced in the small intestine, while the emetic form—often called 'fried rice syndrome'—is caused by a heat-stable toxin called cereulide. Unlike most bacterial toxins, cereulide is produced by nonribosomal peptide synthesis and can withstand temperatures as high as 121 °C for 90 minutes. This makes reheating contaminated food ineffective at neutralizing the poison. Although most cases are self-limiting, severe infections can lead to sepsis or, in rare instances, fatal hepatic failure.

Beyond its role as a pathogen, B. cereus is a versatile biological actor. It possesses a genome of over 5 million base pairs, encoding a vast array of metabolic enzymes and defense mechanisms. Some strains act as probiotics, reducing harmful bacteria in animal guts, while others show promise in ecological bioremediation by breaking down heavy metals or keratinous waste. Researchers have even identified strains that produce polyhydroxybutyrates (PHBs), suggesting a future role for the bacterium in the production of biodegradable plastics. Its ability to adapt—whether by up-regulating genes like arcA in acidic environments or using quorum sensing to coordinate virulence—makes it a subject of intense scientific study.

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