Question

fifty two colonies grew in nutrient agar from 0.1 ml of undiluted sample in a standard plate count. how many viable and culturable cells were in the original sample?
52 per ml
520 per ml
10.4 per ml
5.2 per ml
5200 per ml
question 3
how many colonies are required on a plate created from a serial dilution to be statistically accurate?
25 - 250
20 - 250
35 - 350
30 - 350
20 - 200

Explanation:

Step1: Calculate cells per ml

The formula for viable - cell count is \(\text{CFU/mL}=\frac{\text{Number of colonies}}{\text{Volume of sample (mL)}}\). Given the number of colonies \(= 52\) and the volume of the sample \(V = 0.1\space mL\).

$$ \text{CFU/mL}=\frac{52}{0.1} $$

Step2: Simplify the expression

$$ \frac{52}{0.1}=52\times\frac{1}{0.1}=52\times10 = 520 $$

Answer:

For the first question: B. \(520\) per \(mL\)
For the second question: A. \(25 - 250\)