openstax microbiology test bank

Correct Answer: B

Rationale: The correct answer is B: Clostridium tetani. This bacterium produces tetanospasmin toxin, causing tetanus. Clostridium botulinum (choice A) produces botulinum toxin, leading to botulism. Bacillus anthracis (choice C) causes anthrax, not tetanus. Staphylococcus aureus (choice D) can cause various infections, but not tetanus. Therefore, only Clostridium tetani is the causative agent of tetanus.

Correct Answer: A

Rationale: The correct answer is A: Antitoxic passive immunity. Antibotulinic serum contains pre-formed antibodies against the botulinum toxin, providing immediate protection to the patient. This is passive immunity as the patient does not produce their antibodies but receives them externally. Choice B is incorrect as botulism is not an infection, so the patient does not develop infection immunity. Choice C is incorrect because active immunity involves the body producing its antibodies after exposure to an antigen, which is not the case here. Choice D is incorrect as antimicrobic immunity relates to protection against microbes, not toxins like in botulism.

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. This bacterium is known to form highly resistant spores that can survive for long periods in soil. Bacillus anthracis causes anthrax, a dangerous disease that can be transmitted to humans and animals. The other choices, Francisella tularensis, Brucella abortus, and Yersinia pestis, do not form spores as resistant as Bacillus anthracis. Therefore, only Bacillus anthracis is likely to have survived in the soil of the old burial ground for animal refuse for over 50 years.

Correct Answer: A

Rationale: The correct answer is A: 4 and 250. Coli index is calculated by dividing the number of red colonies by the volume of water analyzed, which gives 2 red colonies / 500 ml = 4. Coli titer is the reciprocal of the coli index, so it is 1 / 4 = 250. This indicates the concentration of coliform bacteria in the water sample. Choices B, C, and D are incorrect as they do not follow the correct calculation steps for determining the coli index and coli titer. B has the correct coli index but incorrect coli titer. C and D have the values reversed, leading to incorrect results.

Correct Answer: B

Rationale: The correct answer is B: Protection against phagocytosis. The bacterial capsule is a protective layer outside the cell wall that helps bacteria evade phagocytosis by the host immune system. It acts as a physical barrier against immune cells like macrophages and neutrophils, allowing the bacteria to survive and multiply in the host. Energy production (A), DNA replication (C), and protein synthesis (D) are essential cellular functions but are not directly associated with the major function of the bacterial capsule, which is protection against phagocytosis.