Question

station 23 if 150 clear zones were counted on a tsa plate after poured with 0.2 ml of a 1:1000 dilution of phages, e. coli and the mixture containing soft agar, how many bacteriophages are in the original undiluted sample? (show your work, include unit) 24 what are the clear zones on the plate in the question above called?

Explanation:

Step1: Recall phage titer formula

Phage titer = $\frac{\text{Number of clear zones}}{\text{Volume plated (ml)} \times \text{Dilution factor}}$

Step2: Plug in values

Number of clear zones = 150, Volume plated = 0.2 ml, Dilution factor = $\frac{1}{1000}$
Phage titer = $\frac{150}{0.2 \times \frac{1}{1000}}$

Step3: Calculate denominator

$0.2 \times \frac{1}{1000} = 0.0002$

Step4: Compute titer

$\frac{150}{0.0002} = 750000$

Clear zones formed by bacteriophages lysing E. coli on a bacterial plate are defined as plaques.

Answer:

750000 bacteriophages/ml