You count 130 colonies on a bacterial plate made from diluti

You count 130 colonies on a bacterial plate made from diluting an overnight culture of E. Coli through the following serial solutions: 100 fold. 100 fold, 10 fold. You plated 0.1 mL. What was the original concentration of viable bacterial cells in your culture in cells/mL? Several mutants of Neurospora are isolated, all of which require compound G for growth. The compounds (A to E) in the biosynthetic pathway to G are known, but their order in the pathway is not known. Each compound is tested for its ability to support the growth of each mutant (1 to 5). In the following table a plus sign indicates growth and a minus sign indicates no growth. A. What is the order of compounds in the pathway, and at what point in the pathway is each mutant blocked? B. Would a heterokaryon composed of double mutants 1.3 and 2, 4 grow on minimal medium? C. What about a heterokaryon of the double mutants 1, 3 and 3, 4?

Solution

5. The total dilution made from the original solution is 10-5 and 0.1ml of this solution was plated on the agar.

The bacteria count was 130

The number of bacteria / ml can be calculated by

130 x 5 (Dilution factor) / 0.1 = 6500 cells / ml

6.

A. The order of the compounds is C B A D E G