1).A 0.0000001 dilution is performed on a culture of bacteria in order to perfor

Question

1).A 0.0000001 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 260 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.

2) How many microliters of original sample are required to produce a final dilution of 10-1 in a total volume of 1 mL?

1 microliter is 10-6 L or 10-3 mL.

3)A 10-9 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 81 colony forming units grow on the plate.

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 = 260 CFU (Colony Forming Units)

Bacteria in single mL of the originial culture = 260 * (1/0.00000001) = 26,000,000,000 = 0.26 * 1011

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