| 21. | Which of the following method can be used to determine the number of bacteria quantitatively? |
| a. | Streak-plate |
| b. | Spread-plate |
| c. | Pour plate |
| d. | Pour-plate and spread plate |
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Answer: (d).Pour-plate and spread plate
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| 22. | Dilution of the mixed culture is a common step in all the three methods: the streak-plate,the spread-plate and the pour-plate technique. |
| a. | True |
| b. | False |
| c. | May be |
| d. | Can't say |
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Answer: (b).False
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| 23. | Which of the following are not performed in lyophilization? |
| a. | agar slant is covered with mineral oil |
| b. | cell suspension is frozen at -60 degree to -78 degree C |
| c. | vials are connected to high-vacuum line |
| d. | bacterial sample is dehydrated |
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Answer: (a).agar slant is covered with mineral oil
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| 24. | Which of the following is a function of cryoprotective agents? |
| a. | for long-term preservation of cultures |
| b. | prevents cell damage due to ice crystal formation |
| c. | prevents formation of ice |
| d. | to trap the liquid nitrogen |
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Answer: (b).prevents cell damage due to ice crystal formation
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| 25. | What is the temperature of liquid nitrogen? |
| a. | -120 degree C |
| b. | 0 degree C |
| c. | -150 degree C |
| d. | -196 degree C |
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Answer: (d).-196 degree C
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