This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Microorganisms Control by Physical Agents – Fundamentals of Control”.
1. In which of the following situations will the logarithmic plot of survivors be constant?
a) physiological conditions are different
b) cells of microbial population vary in size
c) age and physiological conditions are uniform
d) temperature conditions are different
Explanation: Logarithmic plot reveals that the death rate is constant when all conditions are strictly uniform, including the age and the physiological condition of all the microorganisms in the population.
2. A suspension of E.coli exposed to heat treatment may yield a greater number of survivors if a plating medium of _____________ is used.
b) trypticase soy agar
c) deoxycholate agar
d) potato dextrose
Explanation: A suspension of E.coli exposed to heat treatment may yield a greater number of survivors if a plating medium of trypticase soy agar is used rather than a medium containing bile salts such as deoxycholate agar.
3. We require less time to kill the population of many cells.
Explanation: It takes time to kill the population and if we have many cells, we must treat them for a longer time to be reasonably sure that all of the bacteria are dead.
4. The effectiveness of heat in killing microorganisms is much greater in _____________
d) acid and alkali
Explanation: The environment has a profound influence on the rate as well as the efficacy of microbial destruction. The effectiveness of heat is much greater in acid than in alkali material.
5. A high concentration of which of the following compounds in the material generally increases the thermal resistance of microorganisms?
Explanation: The consistency of the material will markedly influence the penetration of the agent and high concentration of carbohydrates generally increases the thermal resistance of organisms.
6. Which of the following show the maximum resistance to physical and chemical agents?
b) Mold spores
c) Bacterial spores
Explanation: In spore forming species, the bacterial spores are extremely resistant in comparison to growing vegetative cells to physical and chemical agents.
7. How much time is required by the young cells to be killed by a lethal agent?
a) 24 hours
b) 3-4 hours
c) 30 mins
d) 5 mins
Explanation: The young cells are all killed within 25 minutes but a considerable part of the more resistant, older cells still survives. Young, actively metabolizing cells are apt to be more easily destroyed than old, dormant cells.
8. Which of the following actions are not affected by antimicrobial agents?
a) cell wall synthesis
b) nucleic acid synthesis
c) protein synthesis
d) capsule formation
Explanation: Antimicrobial agents inhibit or kill microorganisms by any of these actions like damaging cell wall synthesis, inhibiting protein or nucleic acid synthesis and inhibition of enzyme action.
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