Bacillus Cereus

Seriously..... B. CEREUS

By: Lauren Bernard

Bacillus cereus is a gram positive bacteria, and is streptobacillus. The bacteria are rod-shaped, and line up and form chains. B. cereus contains some strains that can cause food borne illness in humans, which is transmitted when food is improperly cooked. This leads to nausea, vomiting, and diarrhea. The good thing is people usually get better on their own, but for dehydration drink lots of water. B. cereus also contains some strains that can be helpful as probiotics for animals. These strains reduce salmonella in the intestines and cecum in animals such as chickens, rabbits, and pigs.

Gram Stain Results

Bacillus Cereus is gram positive, which means that it is has of one thick layer of peptidoglcan as the cell wall, and it appears purple under a microscope. Gram positive bacteria soak up the crystal violet, which is one way you can tell what type of gram stain you have. Gram negative has two layers to their cell wall, besides the thin peptidoglycan layer there is a lipid-carbohydrate layer, and the peptidoglycan layer soaks up the safranin which makes it look red under a microscope.

Environment and Metabolism

B. cereus is a motile bacteria which means when it is put in a tube of MIO agar in one place after 24 hours it will have moved to find food in different places of the tube. B. cereus also tested positive in our methyl red test, which means it produces acidic waste products. In our hemolysis test we found that B. cereus is beta, meaning when put in a sheep blood agar plate it digest all of the hemoglobin. The ideal temperature to grow B. cereus best is 30 degrees, but B. cereus is aerobic so remember to give it oxygen.

Antibiotic Sensitivity

Bauer-Kirby test were conducted on B. cereus with three antibiotcs; tetracycline, chloramphenicol, and streptomycin. Along with that tested were how well hand sanitizer kills B. cereus. After 24 hours I found that chloramphenicol worked best, then streptomycin, and then tetracycline. Surprisingly, hand sanitizer worked the least. I think chloramphenicol worked the best due to the fact that it uses the protein synthesis method to make the bacteria unable to reproduce. Chloramphenicol is also a gorillacillin, meaning it is only used for life threatening purposes.

Pictures

B. Cereus under a microscope
B. Cereus under a microscope

Non-Motile (left) vs. Motile (right)
Non-Motile (left) vs. Motile (right)

Comedic image of an idea of foodborne illness
Comedic image of an idea of foodborne illness

References