Question

At 4 PM, A600 of your yeast culture is 1.0. You want to harvest 10 mL culture of yeast cells at A600 of 1.0 at noon in the next day.You know that yeast doubles every 2.5 h under the same growth conditions used. How much volume of a 4 PM culture would you need to inoculate into a fresh 10 mL medium assuming that 100% of 4 PM culture cells are alive?

Answer 1

The O.D. of 1.0 at 600nm for yeast corresponds to 0.8 -3 X 107 cells/mL. Assume that it is the highest value of 3 X 107 cells/mL.

The requirement is 10 mL of 3 X 107 cells/mL at noon on next day.

Number of cells required = 3 X 107 cells/mL X 10 ml= 3 X 108 cells

Generation time = time/ number of generations

2.5 h= 20 hr/n

n=8

b= Final number of cells= 3 X 108 cells/mL

B= Initial number of cells = ?

Final number of cells (b) = Initial number of cells x 2n (for binary fission)

3 X 108 cells = B X 28

B=3 X 108 cells/256

B= 0.0117 X 108 cells= 1.17 X 106 cells

O.D. of 1.0= 3 x 107 cells/mL

3 X 107 cells= 1ml

1.17 X 106 cells = ?

Volume of cells to be inoculated= 1.17 x 106 cells/3 X 107 cells= 0.039 mL= 37 microliters