A 10 -7 is performed on a culture of bacteria in order to perform viable plate c

Question

A 10-7 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 74 colony forming units grow on the plate.

How many bacteria are in a single mL of the original culture? Express your answer to two decimal places using exponential notation.

Since only 0.1 mL is put on the plate, this counts as an extra dilution!!!

Any time less than 1 mL is transfered, a dilution is being performed.

Any time more than 1 mL is transfered, a concentration is being performed.

Explanation / Answer

ANSWER 1).
Initial dilution of culture of bacteria = 0.0000001
Volume of initial dilution plated = 0.1 mL
Total dilution = 0.0000001 * 0.1 = 0.00000001
Colonies obtained = 74 CFU (Colony Forming Units)

Bacteria in single mL of the originial culture = 74 * (1/0.00000001) = 7400,000,000 = 0.74 * 1010

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