how to dilute from 4.16X10^9 cfu/ml TO 1X10^9 cfu/ml

[paulobrien]

how to dilute from 4.16X10^9 cfu/ml TO 1X10^9 cfu/ml

[lynnsamuelson]

To do this dilution you first need to calculate the amount of the concentrated (4.16x10^9 cfu/mL) you need to mix with the other buffer/water/solvent to result in a final concentration of 1x10^9 cfu/mL. I'm going to assume you would like a final volume of 100 mL. If this is not correct, then you will need to scale the result.

4.16 cfu*10^9/mL * x mL/100mL = 1 cfu*10^9/mL

Solving the above equation, you get x = 24 mL. This means that to do the dilution to a final volume of 100 mL you will need to mix 24 mL of the 4.16 cfu*10^9 solution with 76 mL of your diluting agent (water, buffer or another solvent).

Best practice in dilutions is to:

1) add some (say ~half) of the buffer(water/solvent) to your graduated cylinder (or container you are mixing in)
2) add in the solution you are diluting. Do this slowly in case a reaction occurs.
3)Fill to the the final dilution value (in this example 100 mL) with buffer/water/solvent.

Note: Read the safety precautions on the agent you are diluting to ensure that it is compatible with the diluting agent.