microbiology chapter 13 test bank

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. Parvovirus B19 is a single-stranded DNA (ssDNA) virus. 2. The prefix "parvo-" indicates small size, characteristic of ssDNA viruses. 3. ssDNA viruses replicate in the host cell by converting their ssDNA genome into double-stranded DNA (dsDNA). 4. Therefore, the correct answer is A: Its genome consists of dsDNA. Summary of why other choices are incorrect: B: Parvovirus B19 is a non-enveloped virus, making choice B incorrect. C: Parvovirus B19 has a linear ssDNA genome, not segmented, making choice C incorrect. D: Parvovirus B19 has two structural proteins - VP1 and VP2, making choice D incorrect.

Correct Answer: C

Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel. A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels. D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.

Correct Answer: D

Rationale: The correct answer is D: S phase. During the S phase of the cell cycle, DNA replication takes place to ensure each daughter cell receives a complete set of genetic material. This phase is characterized by the synthesis of new DNA strands. In contrast, choices A, B, and C (G phase, Prophase, Metaphase) are not associated with DNA replication. The G phase is a period of cell growth, Prophase is the initial stage of mitosis, and Metaphase is when chromosomes align. Therefore, the S phase is the specific stage where DNA replication occurs, making it the correct answer.

Correct Answer: A

Rationale: The correct answer is A because the NSP4 nonstructural protein of rotaviruses indeed acts in a toxic-like manner by disrupting calcium homeostasis, leading to diarrhea. Choice B is incorrect as rotaviruses can cause significant disease in infants, but not typically in adults. Choice C is incorrect as rotaviruses are resistant to stomach acid. Choice D is incorrect as rotaviruses cause a net secretion of water and loss of ions, contributing to diarrhea.

Correct Answer: C

Rationale: The correct answer is C because Rickettsia requires living cells for growth and replication. Chick embryos, cell cultures, and lab animals provide a suitable environment for Rickettsia isolation. Skin-allergy tests (A) and serological methods for proving antibodies (B) are not directly used for isolating Rickettsia as they do not support the growth of the bacteria. "None of the above" (D) is incorrect as option C involves the appropriate methods for isolating Rickettsia.