Spores are destroyed by:

Correct Answer: A

Rationale: The correct answer is A because spores are heat-resistant and require high temperatures for destruction. Autoclaving at 121°C for 15-20 minutes ensures spore destruction due to the high pressure and temperature. Choice B (heating to 80°C) is insufficient to destroy spores. Choice C (boiling at 100°C for 10 minutes) is also inadequate as spores require higher temperatures for elimination. Choice D (None of them) is incorrect as autoclaving is the standard method for spore sterilization.

Correct Answer: B

Rationale: The correct answer is B because the capsule of bacteria is mainly composed of polysaccharides or polypeptides. This outer layer helps bacteria evade the host's immune system and protects them from desiccation. Peptidoglycan (choice A) is a component of the bacterial cell wall, not the capsule. Flagellin (choice C) is a protein component of the bacterial flagella, not the capsule. Choice D is incorrect as the capsule is indeed composed of polysaccharides or polypeptides.

Correct Answer: A

Rationale: The correct answer is A: Neisser. Bacterial capsules can be stained using the Neisser staining method because it specifically targets the capsule, making it visible under a microscope. Neisser staining involves using a combination of acidic and basic dyes to highlight the capsule structure. This method helps differentiate the capsule from the bacterial cell, aiding in the identification and study of capsules. Choices B, C, and D are incorrect because Cleat and Müller staining methods are not commonly used for staining bacterial capsules, and "None of the above" is incorrect as Neisser staining is a valid method for capsule staining.

Correct Answer: B

Rationale: Gas gangrene is a severe condition primarily caused by Clostridium perfringens, making option B the correct answer. Clostridium perfringens is an anaerobic bacterium that produces toxins leading to tissue destruction and gas formation in the affected area. This bacterium thrives in environments with low oxygen levels, such as deep wounds. Option A, Clostridium difficile, is not the cause of gas gangrene. Clostridium difficile is known for causing antibiotic-associated diarrhea and colitis. Option C, Clostridium tetani, is responsible for tetanus, a condition characterized by muscle stiffness and spasms due to the bacterium's neurotoxin. Therefore, it is not associated with gas gangrene. Understanding the specific bacteria causing different infections is crucial in microbiology. Knowing the characteristics, pathogenicity, and typical presentations of different bacteria can aid in accurate diagnosis and appropriate treatment. In the case of gas gangrene, recognizing Clostridium perfringens as the causative agent helps healthcare professionals implement timely interventions to prevent further tissue damage and systemic complications.

Correct Answer: A

Rationale: Rationale: 1. Listeria monocytogenes is a Gram-positive bacterium known for causing foodborne illnesses. 2. Gram-negative bacteria have a different cell wall structure than Gram-positive bacteria, making choice A correct. 3. Choice B is incorrect as Listeria monocytogenes is not encapsulated or sporulating. 4. Choice C is incorrect as Listeria monocytogenes does have a cell wall. 5. Choice D is incorrect as Listeria monocytogenes is indeed a Gram-positive coccobacilli.