You are doing an experiment involving antibiotic resistance in your study bacteria. This organism grows well on LB - Miller agar
plates. You want to make 50 plates (assuming 25ml/plate) of LB-Miller at 1.5% agar concentration. Twenty-five of these plates will be plain, the other 25 need to contain 50 micrograms/ml of Gentamycin for your resistance experiments. You have a stock solution of Gentamycin at a concentration of 5 mg/ml. How would you go about making your plates
The stock solution of Gentamycin has a concentration of 5 mg/ml while each plate needs to contain 50 micrograms/ml of Gentamycin.
5 mg/ml = 5000 micrograms/ml
There is a need to dilute the stock antibiotic solution in order to arrive at 50 micrograms/ml. Using the dilution principle;
m1v1 = m2v2
5000 x 1 = 50 x v2
v2 = 5000/50 = 1000 ml
<em>Hence, in order to prepare 50 micrograms/ml, 1 ml of the stock Gentamycin should be taken and diluted with 999 ml of distilled sterilized water. 1 ml of the diluted Gentamycin will then be added to each agar plate while they are still in the molten form at a warm temperature.</em>
