QUESTIONS Completion 1. Using 99-ml dilution blanks (only), draw a scheme that w

Question

QUESTIONS Completion 1. Using 99-ml dilution blanks (only), draw a scheme that would yield between 30 and 300 colonies from an original sample that contains 4.7 × 104 cells/mL 2. What is the minimum number of pipettes you need to achieve one plate with between 30 and 300 colonies in that dilution scheme? 3. Why are plates containing between 30 and 300 colonies the only ones counted? 4. Why must pipettes be changed between dilutions? 5. Name two methods commonly used to plate serial dilutions and

Explanation / Answer

4. Pipettes should be changed between dilutions in order to avoid entrance of bacteria that are stuck in the previous pipette. This practice enhances the accuracy of the result.

5. Streak plate and spread plate are the two methods commonly used to plate serial dilutions.

6. The young cells could have died, or wrong sample might be inoculated.

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