Refer to the following graph to answer questions 1-5 1. What is the generation t
ID: 57156 • Letter: R
Question
Refer to the following graph to answer questions 1-5
1. What is the generation time (g) of this culture?
2. What is the growth rate constant (?) of this culture?
3. A sample of this culture taken at 10h is diluted by a factor of 106X, after which 0.1 ml are spread on a plate. How many CFUs are predicted?
4. A 0.1ml sample taken at 1h is applied to the counting chamber of a hemacytometer. What would be the average number of cells expected in a square with the following dimensions: 1.0mm X 0.2mm X 0.01mm?
5. A sample taken at 6h had an optical density 0.4. What would be the predicted optical density at 8h?
Explanation / Answer
1. The mean generation time or doubling time is 5 hrs. Since doubling time is time required to double the population size in graph it has taken from 2 hrs to 7 hrs Hence 7-2 = 5 hrs.
2. Rate constant K = 1/g = 1/5 = 0.2
3. A sample of this culture taken at 10h is diluted by a factor of 106X, after which 0.1 ml are spread on a plate. How many CFUs are predicted?
The CFU at 10 h in graph is 1.2 X 107/ml. Since it is diluted by 106 X and only 0.1 ml is taken 106 X 10 = 1060 times.
Hence CFU will be 1.2 X 10 7/ 1060 = 7.5 X 105