Which gram-positive bacteria are spore formers?

• A. Staphylococcus aureus
• B. Clostridium botulinum, Clostridium perfringens, and Bacillus cereus
• C. Listeria monocytogenes
• D. Lactobacillus acidophilus

Answer: (B)

Spore formation is a feature of certain Gram-positive bacteria in the Bacillus and Clostridium genera. These endospores are extremely resistant and can survive harsh conditions, which is a key point in food safety and microbial risk.

The organisms listed as spore-formers—Clostridium botulinum, Clostridium perfringens, and Bacillus cereus—are all Gram-positive rods that produce endospores. That combination makes them the correct group for this question.

Other options include bacteria that are Gram-positive but do not form spores. Staphylococcus aureus is a Gram-positive cocci that causes food poisoning mainly through toxins rather than spore formation. Listeria monocytogenes and Lactobacillus acidophilus are Gram-positive rods that do not form spores; they have other roles in food safety and fermentation but aren’t spore-formers.