Bacillus Cereus: Morphology & Characteristics

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  • 0:03 ''Bacillus Cereus'' &…
  • 1:15 ''Bacillus Cereus'' Morphology
  • 1:40 ''Bacillus Cereus'' Endospores
  • 2:55 Lesson Summary
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Lesson Transcript
Instructor: Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

Bacillus cereus is an endospore-forming bacterium that can cause food poisoning. If food has been left at room temperature too long, the endospores can begin to replicate into normal bacteria.

Bacillus Cereus & Food Poisoning

Have you ever been to a party that served food? When you first arrive, everything is fresh and at the right temperature. But as the hours pass, and you're enjoying a room-temperature mini-quiche, you can't help but wonder if it's still safe. You decide to risk it, eat the quiche, and wake up in the morning regretting your decision.

Food that has been left out for too long can allow a bacterium called Bacillus cereus to grow. This is different from more well-known food-poisoning bacteria, such E. coli, Listeria, or Salmonella, which can cause large outbreaks. Like other types of infectious bacteria, B. cereus produces toxins. As the name implies, toxins are not good for you; they are proteins that make you sick.

There are two types of B. cereus food poisoning. One type causes diarrhea about 4 to 16 hours after exposure. Many different types of food, like meats, vegetables, and dairy products, can harbor this type of B. cereus. The other, less common type causes nausea about 1 to 5 hours later. This type is normally associated with rice. The main underlying factor for both types of B. cereus food poisoning is improperly stored food.

Bacillus Cereus Morphology

Morphology describes what shape bacteria have. The most common shapes are cocci, which are round balls; bacilli, which are rods; and spirochetes, which are corkscrews. B. cereus is classified based on how it looks under a microscope, just like most other bacteria species. Bacillus refers to bacteria that have a rod-like shape; sort of like a rectangle with rounded edges.

Bacillus Cereus Endospores

The question remains, though, how does B. cereus cause food poisoning? It's already been mentioned that B. cereus is found in food that has been left out too long, but where does it come from? B. cereus is found in the environment - in soil, on vegetables, in dairy products. However, it's not the normal form of happily replicating B. cereus found on these things. B. cereus, like other closely related species, can form endospores.

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