1Why must serial dilutions of the samples be performed befor

1.Why must serial dilutions of the samples be performed before they are plated on the petri plates?

a.To dilute out the serum, which will inhibit bacterial growth on the plates.

b.to allow for optimal utilization of the nutrients in the growth media.

c.To prevent overgrowth on the plates and allow for countable number of bacterial colonies.

d.all of the above

2. Which of the following equation for calculating the number of colony-forming units/ml (cfu/ml)?

a.#colonies x dilution=cfu/ml

b.#colonies / dilution=cfu/ml

c.#colonies x % serum x dilution=cfu/ml

d.#colonies x %serum/ dilution= cfu/ml

3.The term \"colony-forming units/ml\" refers to which of the following?

a.The number of bacteria present in 1 ml of serum

b.the number of bacteria present on an agar plate

c.the ration of bacteria tothe serum in the sample

d.the numberof bacteria per ml as represented by the number of colonies growing on an agar plate

1.C

The other two statements are no where related with the dilution.

2. C

cfu/ml = (no. of colonies x dilution factor) / volume of culture plate

volume of culture plate means the percentage of the media plated on the plate

3.D

The number of bacteria per ml as represented by the number of colonies growing on an agar plate