S- A disinfectant should be used in your work area a) before you begin latb b) a

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S- A disinfectant should be used in your work area a) before you begin latb b) after a live cutare spill c) after you finish working d) all of the above 9- A loop or a needle is sterilized by inserting it into a Bunsen burner until its red hot. This will a coagulate any contaminating organisms present b incinerate any contaminating organisms present c. activate any contaminating organisms present d. all of the above 10-Why is a stain added to a microbe? A. B. Recognize the morphology of cells To visualize internal structures C. D. Make the cells easier to see under them he microscope All of the above 11- The recommended biosafety level(s) for handling microorganisms represent A. the potential of the agent to cause disease B. the conditions under which the agent should be safely handled C. Both A and B are correct D. None of the above is applicable 12-The recommended biosafety levels (BSL) for micro-organisms are described below. Which of the following is related to BSL-4? Agents that can cause diseases that do not respond to antimicrobial therapy or to vaccines in healthy adults Agents that pose only moderate risk in healthy adults but not likely to spread throughout the community, and readily treatable Agents that can cause disease in healthy adults that can spread very easily throughout the community though can be readily treatable Agents not likely to pose a disease risk to healthy adults A. B. C. D. 13-Which reagent functions as a decolorizer in the Gram stain? A. Crystal violet B. lodine C. Copper sulfate D. Alcohol 14-What is the mordant used in the Gram stain ?. [odine B. Crystal violet C. Safranin D. Alcohol 15-In the Schaeffer-Fulton method, malachite green is use to stair A. B. C. D. Vegetative portion of the cell Capsule Endospores The fungi

Explanation / Answer

Ans. #8. Correct option- d. all of the above. A disinfectant is applied on the working area before and after the lab work to eliminate the chances of contamination to the lab procedures from pre-existing microbes, and to remove the traces of microbes from the working area transferred during work. Moreover, any culture-spill must be disinfected immediately.

#9. Correct option- b. The temperature of Bunsen burner flame is around 15000C. It burns and kills (incinerate) all forms of life from the loop upon incineration.

# Option- a- Incorrect. Coagulation is a process of protein denaturation. Once proteins (enzymes) of a cell are coagulated, it dies due to loss of biological activity of the proteins/enzymes that catalyze most of the cellular metabolism. Moreover, the term coagulation refers to denaturation of protein but not of an organism on a whole. Incineration burns and kills the micorbes but does not coagulates protein or the microbes.

# Option- c, d- Incorrect. See #b.

#10. Correct option- D. Micorbes are generally colorless under microscope. To make them visible under microscope, they are stained with suitable stains. Some stains stain/color the outer surface of the cell (Grams’ stain, acid-fast stain) whereas the other stains colorize the internal structures (endospores in bacteria, nucleus in eukaryotic cell, etc.).

#11. Correct option- C. The recommended biosafety levels (1 through 4) identifies the relative risk of microbes to cause infections – higher is the infectious nature of the microbe, greater would be the biosafety level recommended to be adopted during handling it. It also outlines the SOP to handle the micorbes at different safety levels.

#12. Correct option- A. BSL-4 outlines the SOP to handle life-threatening microbes against which no proper treatment (antimicrobial agents or vaccine) is available.

#13. Correct option- D. Alcohol acts as decolorizer.

# Iodine acts as mordant. CV as a primary stain. CuSO4 is NOT used in Grams’ staining.

#14. Correct option- A. Iodine

# Safranin acts as counter-stain.

#15. Correct option- C. It stains endospores.

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