Question

0.2 mls of a 10⁻⁴ dilution of a virus preparation yields 90 plaques. What is the number of PFU per ml in the undiluted virus preparation?

1) 9.0 × 10⁵
2) 4.5 × 10⁶
3) 4.5 × 10⁷
4) 9.0 × 10⁸

Answer 1

The number of PFU per ml in the undiluted virus preparation is 0.01.

Step-by-step explanation:

The number of PFU (Plaque Forming Units) per ml in the undiluted virus preparation can be calculated using the information provided. If 0.2 ml of a 10⁻⁴ dilution yields 90 plaques, this means that each plaque corresponds to 0.002 ml of the original undiluted virus preparation.

To find the number of PFU per ml, we can set up a proportion:

0.002 ml plaque / 0.2 ml diluted sample = X PFU / 1 ml undiluted sample

Cross-multiplying and solving for X, we get:

X = (0.002 ml plaque × 1 ml undiluted sample) / 0.2 ml diluted sample = 0.01 PFU per ml undiluted sample