Question

# A 0.1 dilution is performed on a culture of bacteria in order to perform viable plate...

A 0.1 dilution is performed on a culture of bacteria in order to perform viable plate counts. From the dilution, *0.1 mL* of solution is plated on solid media, and 218 colonies of bacteria grow on the petri dish. Assuming each colony came from a single bacterium, how many bacteria are in a single mL of the original culture? Express your answer to two decimal places using exponential notation.

The correct answer will be 2.18e4. Since 0.1 mL of solution contain 218 bacetria (As each colony came from single bacterium), 1 mL of solution contain 2180 bacterium. But this 1 mL of solution is obtained by 0.1 dilution (diluted the volume 10 times). It means the original solution concentration was 2180 X 10 = 21800. Thus the concentration of original culture was 21800 bacteria per mL.

This 21800 can be sintifically notated in the exponential form as follows:

21800 = 2.18 X 104 = 2.18E4 or 2.18e4

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