A plaque assay is performed beginning with 1 mL of a solution containing bacteri
ID: 162875 • Letter: A
Question
A plaque assay is performed beginning with 1 mL of a solution containing bacteriophages. This solution is serially diluted 5 times by combining 0.1 mL of each sequential dilution with 9.9 mL of liquid medium. Then 0.1 mL of the final dilution is plated in the plaque assay and yields 28 plaques.
What is the initial density of bacteriophages in the original 1 mL? Recall that initial phage density = (plaque number/mL) × (dilution factor).
Enter your answer to two significant digits (for example: 1.1 * 102). plaque-forming units/mL
Explanation / Answer
Answer:
Dilution factor after 5 serial dilutions= 1/10^5
How?
0.1+9.9mL= 1/10 fold dilution
1/10 fold x 1/10 fold x 1/10 fold x 1/10 fold x 1/10 fold =1/10^5 fold dilution
CFU/ml = ?
Dilution factor= 1/10^5
Number of colonies= 28
Volume of sample = 0.1 mL to the plate
cfu/ml = (no. of colonies)/ dilution factor x volume of culture plate
cfu/ml = (28)/ (1/10^6 x 0.1)
cfu/ml = 28 x 10^7
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.