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Which bacteria are capable of forming spores to survive in harsh environments?
- A. Bacillus anthracis
- B. Clostridium botulinum
- C. Both A and B
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C (Both A and B) because both Bacillus anthracis and Clostridium botulinum are capable of forming spores to survive in harsh environments. Bacillus anthracis causes anthrax and forms spores that can survive extreme conditions. Clostridium botulinum causes botulism and also forms spores for survival. Option A (Bacillus anthracis) and Option B (Clostridium botulinum) are incorrect on their own because they only represent one of the bacteria capable of forming spores. Option D (None of the above) is incorrect because it disregards the fact that both bacteria can form spores.
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Autoclaving will usually destroy/inactivate all fungi, bacteria, viruses, and most bacterial spores but will not necessarily eliminate
- A. neurotoxins.
- B. prions.
- C. protozoan cysts.
- D. mycoplasmas.
Correct Answer: B
Rationale: The correct answer is B: prions. Autoclaving, a method of sterilization using high pressure and steam, is effective at destroying most microorganisms including fungi, bacteria, viruses, and most bacterial spores due to denaturation of their proteins and nucleic acids. However, prions are highly resistant infectious proteins that are not easily eliminated by autoclaving. Prions can withstand high temperatures and pressure, making them a challenge to eradicate. Neurotoxins (A), protozoan cysts (C), and mycoplasmas (D) are susceptible to autoclaving and would be destroyed during the process.
The specific binding of HIV to the CD4 surface molecules of the target cells is brought about by:
- A. Gp120
- B. Gp41
- C. Gp32
- D. Gp55
Correct Answer: A
Rationale: The correct answer is A: Gp120. Gp120 is a glycoprotein on the surface of the HIV virus that specifically binds to the CD4 receptor on target cells. This binding is essential for the virus to enter the host cell and initiate the infection process. Gp41 is another glycoprotein on the virus that helps with membrane fusion, not binding to CD4. Gp32 and Gp55 are not involved in the specific binding of HIV to CD4 molecules. So, A is correct as it directly plays a key role in the initial attachment of HIV to target cells.
Bacteriological inspection of disinfection quality at a pharmacy revealed a microorganism in an utility room (in the sink). The microorganism has the following properties: mobile nonspore-forming gram- negative bacteria that form capsular substance, grow well on ordinary nutrient media, secrete the blue-green pigment. This microorganism is most likely to be of the following genus:
- A. Pseudomonas
- B. Proteus
- C. Clostridium
- D. Shigella
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas.
Rationale:
1. Mobile nonspore-forming gram-negative bacteria with a capsule substance indicate Pseudomonas.
2. Pseudomonas grow well on ordinary nutrient media, matching the description.
3. The secretion of a blue-green pigment is a characteristic feature of Pseudomonas.
4. Proteus is a gram-negative bacterium but does not match all the given properties.
5. Clostridium is a gram-positive bacterium that forms spores.
6. Shigella is a gram-negative bacterium but does not have the other characteristics mentioned.
Therefore, based on the properties described, the most likely genus of the microorganism is Pseudomonas.
Bacteria that use organic compounds as the source of both carbon and energy are referred to as:
- A. photoautotrophs
- B. chemoautotrophs
- C. photoheterotrophs
- D. chemoheterotrophs
Correct Answer: D
Rationale: The correct answer is D: chemoheterotrophs. Chemoheterotrophs use organic compounds as both their carbon source and energy source. They obtain energy by breaking down organic molecules through cellular respiration. Photoautotrophs (A) use light energy to produce organic compounds, chemoautotrophs (B) use inorganic compounds for energy, and photoheterotrophs (C) use light energy but require organic compounds as a carbon source. Therefore, chemoheterotrophs best describe bacteria that obtain both carbon and energy from organic compounds.
The causative agent of typhoid fever is:
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella typhi
- D. Escherichia coli
Correct Answer: C
Rationale: The correct answer is C: Salmonella typhi. Typhoid fever is caused by the bacterium Salmonella typhi, specifically transmitted through contaminated food and water. Shigella dysenteriae causes bacillary dysentery, Vibrio cholerae causes cholera, and Escherichia coli can cause various gastrointestinal illnesses, but not typhoid fever. Identifying the causative agent is crucial for effective treatment and prevention strategies.