2. Phage Titer Problems (a) You observe 78 plaques on an agar plate PFU/ml in th
ID: 217129 • Letter: 2
Question
2. Phage Titer Problems (a) You observe 78 plaques on an agar plate PFU/ml in the original phage sample? which received a phage dilution of 10-4. What is the (b) An agar plate which received a phage dilution of 10 produced 298 plaques after incubation, while the 102 plate produced 31 plaques. Since both plates are countable, use data from both to determine the PFU/ml in the original phage sample? (c) A phage sample has a PFU/ml of 1.66 x 103. Assuming a 1:10 dilution series and plating as we did in class, which plate should be the countable plate? In other words, which plate is likely to yield 166 plaques? (d) You have used a phage titer procedure to determine the titer of a phage sample to be 100,000 PFU/ml. You now want to use this phage sample to conduct an experiment, and you need to make sure each trial of the experiment uses the same phage concentration of phage: 100 PFU/ml. Describe and/or diagram how you will use the original phage sample to prepare a diluted sample with the desired PFU/ml for your experiment. In your description/ diagram, you MUST show exactly how much phage solution and how much sterile broth you need. 149Explanation / Answer
(a)
Original PFU/ml = ?
Dilution factor = 10^-4
Number of plaques= 78
Volume of sample =0.1 mL to the plate
cfu/ml = (no. of plaques)/( dilution factor x volume of culture plate)
cfu/ml = (78)/ (10^-4 x 0.1)
pfu/ml = 78x 10^5 pfu/mL
(b)
From plate with 298 colonies
Original PFU/ml = ?
Dilution factor = 10^-1
Number of plaques= 298
Volume of sample =0.1 mL to the plate
cfu/ml = (no. of plaques)/( dilution factor x volume of culture plate)
cfu/ml = (298)/ (10^-1 x 0.1)
pfu/ml = 2.98x10^4 pfu/mL
From plate with 31 colonies
Original PFU/ml = ?
Dilution factor = 10^-2
Number of plaques= 31
Volume of sample =0.1 mL to the plate
cfu/ml = (no. of plaques)/( dilution factor x volume of culture plate)
cfu/ml = (31)/ (10^-2 x 0.1)
pfu/ml = 3.1 x10^4 pfu/mL4
Therefore the original stock is ~ 3x 10^4pfu/mL
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