You have removed a volume of a culture of E. coli during exponential growth in o
ID: 227068 • Letter: Y
Question
You have removed a volume of a culture of E. coli during exponential growth in order to measure the viable cell count. If the absorbance reading was 0.9, estimate the maximum dilution factor you would need in order to obtain between 30 and 300 colonies on a plate spread with 0.1 ml of the dilution. Assume that there are 107 cells/ml in one absorbance unit. Submit Answer Tries 0/99
You have removed a volume of a culture of E. coli during exponential growth in order to measure the viable cell count. If the absorbance reading was 0.9, estimate the minimum dilution factor you would need in order to obtain between 30 and 300 colonies on a plate spread with 0.1 ml of the dilution. Assume that there are 107 cells/ml in one absorbance unit. Submit Answer Tries 0/99
Explanation / Answer
Answer:
Absorbance reading = 0.9
One absorbance unit = 107 cells / ml
Concentration of cells = Absorbance reading x Absorbance unit = 0.9 x 107 = 9 x 106 CFU / ml.
*CFU = Colony Forming Units.
Stepwise dilution starting from the initial concentration will be as below:
Thus, we can conclude that a maximum dilution factor of 104 can get 30 - 300 colonies.
1 ml contains 9 x 106 CFU 0.1 ml will contain 9 x 105 CFU 0.01 ml will contain 9 x 104 CFU 0.01 ml will contain 9000CFU 0.001 ml will contain 900CFU 0.0001 ml will contain 90 CFURelated Questions
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