microbiology chapter 10 test bank

Correct Answer: A

Rationale: Rationale: Vibrio cholerae produces the exotoxin responsible for severe diarrhea. It causes cholera by disrupting the normal functioning of the intestines. Clostridium botulinum causes botulism, not diarrhea. Streptococcus pyogenes causes strep throat and skin infections. Salmonella enterica causes food poisoning, not severe diarrhea. Therefore, the correct answer is A.

Correct Answer: A

Rationale: The correct answer is A: Halophiles. Halophiles are bacteria that thrive in high-salinity environments due to their ability to tolerate high salt concentrations. They have adapted mechanisms to maintain osmotic balance and survive in such extreme conditions. Thermophiles (B) thrive in high-temperature environments, not high-salinity. Acidophiles (C) prefer acidic conditions, not high-salinity. Mesophiles (D) grow optimally at moderate temperatures and are not specifically adapted to high-salinity environments.

Correct Answer: B

Rationale: The correct answer is B: Leptospirosis. Spiral-shaped bacteria with loose coils and pointed ends are characteristic of Leptospira interrogans, the causative agent of Leptospirosis. This bacterium is typically found in contaminated water or soil and can infect humans through contact with infected animals or water. Syphilis (Choice A) is caused by the spirochete Treponema pallidum, which has a more tightly coiled shape and does not typically appear loose or pointed. Relapsing fever (Choice C) is caused by Borrelia species, which are also spirochetes but do not have the loose coils and pointed ends described. Lyme disease (Choice D) is caused by Borrelia burgdorferi, which, like Relapsing fever, does not match the morphology described.

Correct Answer: B

Rationale: The correct answer is B: Hepatitis B virus. This is because Hepatitis B virus is a DNA virus, not an RNA virus. The other choices, A (Hepatitis G virus), C (Hepatitis A virus), and D (Hepatitis E virus) are all RNA viruses. Hepatitis B virus is unique as it contains partially double-stranded DNA. DNA viruses replicate through a DNA intermediate, unlike RNA viruses which directly use RNA. Therefore, Hepatitis B virus stands out as the only DNA virus among the given options.

Correct Answer: D

Rationale: The correct answer is D: Agar media. Influenza viruses cannot be isolated in agar media because they require specific conditions present in laboratory animals, embryonated eggs, or cell cultures for successful isolation and propagation. Agar media lack the necessary components and environment needed for influenza virus replication. In laboratory animals, such as mice, the viruses can replicate and cause infection. Embryonated eggs provide a suitable environment for influenza virus growth and isolation due to the presence of necessary nutrients and factors. Cell cultures offer controlled conditions for virus propagation and study, making them a valuable tool in influenza virus research.