Each macrophage has 10 bacteria to eat. There are 1,000,000 macrophages per well

Question

Each macrophage has 10 bacteria to eat. There are 1,000,000 macrophages per well. You will need 10,000,000 E.coli per 200 microliters of cell culture medium. Your initial E.coli concentration is 1 x 10^9 CFU/ml. You have 4 wells to "feed" with E.coli. Calculate the dilution of E.coli(use C1V1=C2V2). Make enough for 5 wells to count for pipetting errors.

50 microliters of E.coli in 950 microliters of media

50  microliters of E.coli in 450 microliters of media

50 microliters of E.coli  in 1.45 ml of media

50 microliters of E.coli in 1.95 ml of media

50 microliters of E.coli in 950 microliters of media

50  microliters of E.coli in 450 microliters of media

50 microliters of E.coli  in 1.45 ml of media

50 microliters of E.coli in 1.95 ml of media

Explanation / Answer

Since, this problem is solved by using C1V1=C2V2, so let's calculate the S2 first.

The question has stated 10,000,000 E.coli per 200 microliters of cell culture. Therefore, for 1ml of cell culture, the amount of E.coli will be 50,000,000. So, the final concentration (S2) is 50,000,000/ml.

The initial concentration (S1) is already given, i.e.,1x10^9/ml.

So, to make a final volume (C2) of 1ml ,

[ C2 x S2 / S1 ] = C1 (the dilution needed)

the dilution needed is 50 microliters in 950 microliters.

So, taking into consideration the pipetting error, this dilution will be enough.

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