Question

1)How many microliters of original sample are required to produce a final dilution of 10^-2 in a total volume of 5 mL?

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

2)A 0.00001 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 197 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.  In exponential notation 540 would be written as 5.40e2. Please use a lower-case letter e.

• 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.

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 118 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. In exponential notation 540 would be written as 5.e2. Please use a lower-case letter e.

• 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.

Answer 1