Below are sample questions from this exam to help you understand the content and format.
Q1: Which biosafety level would be MOST appropriate for a non-pathogenic strain of Escherichia Coli?
Answer Choices:
A. BSL-4
B. BSL-3
C. BSL-2
D. BSL-1
Correct Answer: BSL-1
Rationale:
🔹 BSL-1 — This is correct because non-pathogenic strains of E. coli (such as E. coli K-12) pose minimal potential hazard to laboratory personnel and the environment, so standard microbiological practices without special containment are sufficient—
🔹 BSL-2 — This is incorrect because it is used for moderate-risk pathogens that can cause disease in humans (e.g., pathogenic E. coli, Salmonella), requiring limited access and biosafety cabinets—
🔹 BSL-3 — This is incorrect because it is reserved for pathogens that can cause serious or potentially lethal diseases through inhalation, such as Mycobacterium tuberculosis—
🔹 BSL-4 — This is incorrect because it is used for the most dangerous, high-risk agents (e.g., Ebola virus) that have no available treatment or vaccine
Q2: How is an inoculating loop or needle sterilized prior to use?
Answer Choices:
A. exposure to UV radiation for 15 seconds
B. holding in the hottest part of the Bunsen burner flame until red-hot
C. soaking in 95% ethyl alcohol for several minutes and allowing to air dry
D. dipping into a beaker of boiling water
Correct Answer: holding in the hottest part of the Bunsen burner flame until red-hot
Rationale:
✨ Holding in the hottest part of the Bunsen burner flame until red-hot — This is correct because direct flaming incinerates all microorganisms, ensuring the inoculating loop or needle is sterile before and after use—
✨ Exposure to UV radiation for 15 seconds — This is incorrect because UV light is not reliable for sterilizing small metal instruments; it is used for surface disinfection, not tools—
✨ Soaking in 95% ethyl alcohol for several minutes and allowing to air dry — This is incorrect because alcohol is a disinfectant, not a sterilant; spores and some microbes can survive—
✨ Dipping into a beaker of boiling water — This is incorrect because boiling reduces microbial load but does not guarantee sterilization, especially against spores—
Q3: What would happen to peach juice if we apply heat at >135 oc to it such as in the use of an autoclave?
Answer Choices:
A. It would just be filtered
B. It becomes agitated
C. It would become sterile
Correct Answer: It would become sterile
Rationale:
💥 It would become sterile — This is correct because heating peach juice above 135 °C (such as in an autoclave) kills all microorganisms, including spores, thereby achieving sterilization—
💥 It would just be filtered — This is incorrect because heat does not filter; filtration is a separate physical method of removing microbes without heat—
💥 It becomes agitated — This is incorrect because agitation refers to physical mixing or shaking, not the effect of high-temperature sterilization—
Q4: What is the correct way to open an agar plate to either remove a sample or to inoculate?
Answer Choices:
A. Remove the lid completely and set it on the bench in an upright position.
B. Remove the lid completely, holding it in your hand. not setting it on the bench.
C. Open lid slightly on one side. in a clam-shell fashion.
D. Remove the lid completely and set it on the bench upside down.
Correct Answer: Open lid slightly on one side. in a clam-shell fashion.
Rationale:
🩺 Open lid slightly on one side, in a clam-shell fashion — This is correct because it minimizes exposure of the agar surface to airborne contaminants while still allowing access for inoculation or sample removal—
🩺 Remove the lid completely and set it on the bench in an upright position — This is incorrect because it exposes the agar surface directly to contaminants in the air—
🩺 Remove the lid completely, holding it in your hand, not setting it on the bench — This is incorrect because even though you don’t set it down, the agar is still widely exposed to contamination—
🩺 Remove the lid completely and set it on the bench upside down — This is incorrect because it exposes the agar and also risks contaminating the lid itself—
Q5: When sterilizing your loop in the Bunsen burner, the flame should be colored
Answer Choices:
A. yellow.
B. orange.
C. blue.
D. red.
Correct Answer: blue.
Rationale:
🔶 Blue — This is correct because the hottest, most efficient part of a Bunsen burner flame is the blue cone, which provides the necessary heat to sterilize the loop until red-hot—
🔶 Yellow — This is incorrect because a yellow flame is a “safety flame” with incomplete combustion, cooler, and sooty, making it unsuitable for sterilization—
🔶 Orange — This is incorrect because an orange flame also indicates incomplete combustion and insufficient heat—
🔶 Red — This is incorrect because the flame itself is never red; instead, the loop glows red-hot after being heated in the blue flame—
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