foundations in microbiology test bank

Correct Answer: C

Rationale: The correct answer is C because isolating a defined microorganism in pure culture involves obtaining a single, distinct colony on solid media. This ensures that only one type of microorganism is present in the culture, preventing contamination. Liquid media can harbor multiple organisms, making it challenging to isolate a specific microorganism. Therefore, choice A is incorrect. Choice B is also incorrect as liquid nutrient media does not provide the necessary isolation required for pure culture. Choice D is incorrect because isolating from single colonies on solid media allows for the pure culture of the defined microorganism.

Correct Answer: C

Rationale: The correct answer is C: Streptococcus pyogenes. This bacterium is commonly known as "flesh-eating bacteria" due to its ability to cause severe tissue destruction and necrotizing fasciitis. Streptococcus pyogenes produces toxins that break down skin and muscle tissues. Staphylococcus aureus (A) can cause skin infections but is not typically associated with necrotizing fasciitis. Staphylococcus epidermidis (B) is a normal skin flora and rarely causes infections. Propionibacterium acnes (D) is associated with acne and not known for causing tissue destruction. Therefore, the correct choice is Streptococcus pyogenes due to its unique ability to cause severe tissue damage and necrotizing fasciitis.

Correct Answer: A

Rationale: Step-by-step rationale: 1. The presence of a nucleus with a nuclear membrane indicates eukaryotic cells. 2. Eukaryotes have genetic material in chromosomes made of DNA and proteins. 3. Mitotic division is characteristic of eukaryotic cells. 4. Therefore, the organisms described are eukaryotes. Summary: - Bacteriophages (B) are viruses that infect bacteria. - Prokaryotes (C) lack a nucleus and their genetic material is not organized into chromosomes. - Viruses (D) are not considered living organisms and do not have a nucleus or chromosomes.

Correct Answer: B

Rationale: The correct answer is B because Q-fever is not transmitted only after ticks bite; it can also be transmitted through inhalation of contaminated aerosols. Rickettsia mooseri and Rickettsia provazekii can cause spotted fevers, making choice A correct. Mediterranean fever is associated with a recurrent pattern of fever, not maculopapular rash, making choice C incorrect. "None of the above" is not correct in this case as choice B is incorrect.

Correct Answer: A

Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.