You have a bacterial suspension and you need to dilute it to 0.0010 of the initial concentration so that you can determine the number of colonies per milliliter. The volumes must be between 0.1 and 2 ml. Your final volume must be 1 milliliter.
To dilute the bacterial suspension to a final concentration of 0.0010 of the initial concentration, you will need to perform a series of dilutions using different volumes.
Here's a step-by-step guide to achieve the desired dilution:
1. Calculate the dilution factor: The dilution factor is the ratio of the final volume (1 ml) to the initial volume. In this case, the ratio is 1/initial volume. Since the desired final concentration is 0.0010, the dilution factor would be 0.0010/initial concentration.
2. Determine an appropriate initial volume: Since the volumes must be between 0.1 and 2 ml, choose a volume within this range that would allow for a reasonable dilution factor. For example, if the initial concentration is relatively high, you might choose a smaller initial volume to achieve a larger dilution factor.
3. Calculate the required volume of bacterial suspension: Multiply the dilution factor by the desired final volume (1 ml) to determine the required volume of the bacterial suspension. For example, if the dilution factor is 0.0010 and the initial volume is 0.5 ml, the required volume of the bacterial suspension would be 0.0010 x 1 ml / 0.5 = 0.002 ml.
4. Mix the required volume of bacterial suspension with an appropriate volume of diluent: In this case, to achieve a final volume of 1 ml, subtract the required volume of bacterial suspension from 1 ml. For example, if the required volume of bacterial suspension is 0.002 ml, you would need to add 1 ml - 0.002 ml = 0.998 ml of diluent (e.g., sterile water or buffer) to make up the total volume.
5. Mix the diluted suspension thoroughly to ensure uniform distribution of bacteria.
6. Repeat steps 3-5 if the desired dilution is not achieved, adjusting the initial volume and dilution factor as necessary.
Remember to perform all dilutions using sterile techniques to prevent contamination. Finally, plate a known volume of the diluted bacterial suspension on an appropriate agar medium and incubate under appropriate conditions to allow colony formation. Count the number of colonies and multiply by the appropriate dilution factor to determine the number of colonies per milliliter in the original bacterial suspension.