A liquid culture of E.coli at a concentration of 2x10^(8) cells/ml was diluted s
ID: 36042 • Letter: A
Question
A liquid culture of E.coli at a concentration of 2x10^(8) cells/ml was diluted serially, as shown in the following diagram, and 0.1 ml of cells from the last two test tubes were spread on agar plates containing rich medium. How many colonies do you expect to grow on each of the two plates?
A liquid culture of E.coli at a concentration of 2x10^(8) cells/ml was diluted serially, as shown in the following diagram, and 0.1 ml of cells from the last two test tubes were spread on agar plates containing rich medium. How many colonies do you expect to grow on each of the two plates?Explanation / Answer
Tube no
Volume of culture transferred in ml
Dilution Factor
1
0.1
100
2
0.1
10-2
3
1.0
10-4
4
1.0
10-5
5
1.0
10-6
# of colonies on plate = # CFU in initial stock culture X Amount Plated X Dilution factor
# of colonies on 10-5 dilution plate = 2 x 108 x 0.1 x 10-5 = 2 x 108-1-5 = 2 x 102 = 200 colonies
# of colonies on 10-6 dilution plate = 2 x 108 x 0.1 x 10-6 = 2 x 108-1-6 = 2 x 10 = 20 colonies
Tube no
Volume of culture transferred in ml
Dilution Factor
1
0.1
100
2
0.1
10-2
3
1.0
10-4
4
1.0
10-5
5
1.0
10-6
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