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Bacillus cereus (Food poisoning)
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food poisoning p. 175, 727
spore formation p. 129
Bacillus cereus p. , 136
Bacillus cereus p. , 136
So Bacillus Cereus refers to a rod-shaped bacteria that looks like a wax-candle.
Most often, this bacteria causes food poisoning, but it can also cause more serious infections, mainly in immunocompromised individuals.
B. cereus has a thick peptidoglycan cell wall, which takes in purple dye when Gram stained - so this is a gram-positive bacteria.
Also, it is a motile bacteria, as it has thread-like flagella that can help it swim in a liquid media, or swarm on a solid surface such as culture media.
It’s also aerobic, meaning it requires oxygen for growth.
B. cereus is catalase positive, meaning it produces catalase enzyme.
This can be tested by adding a few drops of hydrogen peroxide to a colony of bacteria, and catalase makes hydrogen peroxide dissociate into water and oxygen, making the mixture foam.
That’s because B. cereus makes a toxin called beta-hemolysin, that causes complete lysis of the hemoglobin in the red blood cells, making the blood agar change color from red to transparent yellow around the colonies
Finally, Bacillus Cereus is a spore-forming bacteria, so it can undergo endosporulation when it feels threatened by the environment, like when the temperature becomes too high or too low, in case of extreme dryness, or when there’s harmful radiation around.
Endosporulation means that the bacteria starts by replicating its DNA, and then it forms a wall inside the cell, isolating a portion from the rest of the cell - let’s call it the mother cell.
The forespore then invaginates into the mother cell and gets completely engulfed by it.
Inside the dying mother cell, the forespore loses water and accumulates calcium, and at the same time gets wrapped in a super tough cortex from the dying mother cell.
Bacillus cereus is a rod-shaped, spore-producing, gram-positive bacterium that's known to cause food poisoning. It can contaminate a variety of foods, including cooked rice, pasta, and potato salad. As a spore-forming bacteria, Bacillus cereus can survive for long periods outside of the body. Symptoms include profuse watery diarrhea, nausea, vomiting, and abdominal cramping. Symptoms usually start within 6 to 15 hours after ingesting contaminated food.
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