Viral capsomeres are composed of subunits called

Correct Answer: B

Rationale: The correct answer is B: protomeres. Viral capsomeres are the building blocks of viral capsids, which are protein coats that enclose and protect the viral genetic material. These capsomeres are made up of smaller subunits called protomeres. Envelopes (A) refer to a lipid membrane surrounding some viruses, not the subunits of capsomeres. Capsids (C) are the protein coats that capsomeres make up, not the subunits themselves. Nucleoids (D) are found in bacterial cells and refer to the region where the genetic material is located, not the subunits of viral capsomeres.

Correct Answer: B

Rationale: The correct answer is B: Clostridium perfringens. This bacterium is associated with myonecrosis/gas gangrene and can produce enterotoxin causing food intoxication. Clostridium septicum (A) is associated with wound infections but not known for food intoxications. Clostridium histolyticum (C) is not typically associated with myonecrosis or food intoxications. Clostridium novyi (D) is known for causing black disease in sheep and cattle, not food intoxications.

Correct Answer: C

Rationale: The correct answer is C: Tularemia. Ticks can transmit tularemia, a bacterial infection caused by Francisella tularensis. Ticks pick up the bacteria when feeding on infected animals and can then transmit it to humans through their bites. Botulism (A) is caused by toxins produced by Clostridium botulinum bacteria, not transmitted by ticks. Anthrax (B) is a bacterial infection caused by Bacillus anthracis, typically transmitted through contact with contaminated animal products. MRSA (D) is a bacterial infection caused by Staphylococcus aureus, commonly transmitted through direct contact with infected individuals or contaminated surfaces, not by ticks.

Correct Answer: A

Rationale: The correct answer is A: Yersinia pestis. Y. pestis is responsible for causing the plague, a severe infectious disease. This bacterium is transmitted via fleas from rodents to humans. It causes bubonic, septicemic, and pneumonic plague. Clostridium difficile causes gastrointestinal infections, Neisseria gonorrhoeae causes gonorrhea, and Pseudomonas aeruginosa can cause various infections but not the plague.

Correct Answer: B

Rationale: The correct answer is B: glycocalyx. The glycocalyx is a matrix formed outside the plasma membrane that consists of glycoproteins and glycolipids. It plays crucial roles in cell-cell recognition, protection, and immune response. Cytoplasm (A) is the gel-like substance inside the cell, not outside. Exoplasm (C) is not a recognized term in biology. Cell wall (D) is a rigid structure found in plant cells, not outside the plasma membrane in all cells.

Correct Answer: D

Rationale: The correct answer is D: components of the gram-negative cell wall. Bacterial endotoxins are lipopolysaccharides found in the outer membrane of gram-negative bacteria. They are released upon bacterial cell lysis and can cause severe immune responses. A: Proteins in the cell wall - This is incorrect because endotoxins are not proteins but rather lipopolysaccharides. B: Secreted into the environment - Endotoxins are not actively secreted but are released upon cell death or lysis. C: Components of the gram-positive cell wall - Gram-positive bacteria do not have an outer membrane with lipopolysaccharides, so endotoxins are not found in the gram-positive cell wall.

Correct Answer: C

Rationale: Step-by-step rationale: 1. The Filoviridae family includes Marburg virus and Ebola virus. 2. Both viruses are characterized by filamentous, enveloped structure. 3. They cause severe hemorrhagic fever in humans. 4. Lassa virus and lymphocytic choriomeningitis viruses belong to Arenaviridae. 5. Chikungunya virus and Sindbis virus are alphaviruses. 6. Crimean-Congo virus and Hantaan virus are bunyaviruses. 7. Therefore, the correct answer is C.

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. The black, painless carbuncle with peripheral vesicular rash is characteristic of cutaneous anthrax. Microscopy showing non-motile Gram-positive rods with a capsule aligns with Bacillus anthracis. The other choices can be eliminated: B: Staphylococcus aureus does not typically form a black lesion or have a capsule. C: Clostridium perfringens causes gas gangrene, not the described lesion. D: Bacillus subtilis is not associated with the specific clinical presentation mentioned.

Correct Answer: A

Rationale: The correct answer is A: Anaerobic infection. The sudden deterioration, bursting pain, edema, foul appearance of wound, and presence of gas are indicative of gas gangrene caused by anaerobic bacteria like Clostridium perfringens. These bacteria thrive in low oxygen environments, such as deep wound tissues. The symptoms align with the classic presentation of gas gangrene, necessitating immediate surgical intervention. Choice B: Aerobic gram-negative, is incorrect because anaerobic bacteria, not aerobic gram-negative bacteria, are responsible for gas gangrene. Choice C: Putrid, is incorrect as it is a general term referring to foul-smelling decay and does not specify the type of infection. Choice D: Aerobic gram-positive, is incorrect as gas gangrene is typically caused by anaerobic bacteria, not aerobic gram-positive bacteria.