Question

you want to set up a 1: 10 dilution series, so that you can plate a 10-1 , 10-2 , and a 10-3 dilution; however, you only have access to two 9 ml dilution blanks. explain how you could accomplish this task with only two blanks

Answer 1

To create a 1:10 dilution series with two dilution blanks, add 1 ml of the sample to the first blank for a 10^-1 dilution, then transfer 1 ml from this to the second blank for a 10^-2 dilution and proceed similarly for the next dilution in a new container.

Step-by-step explanation:

To accomplish a 1:10 dilution series with only two 9 ml dilution blanks, you could use the following method. First, add 1 ml of the original culture to the first 9 ml dilution blank, resulting in a 10-1 dilution. Then, take 1 ml of this first dilution and add it to the second 9 ml blank, creating a 10-2 dilution.

Finally, to achieve the 10-3 dilution, take 1 ml from the second dilution and add 9 ml of sterile broth in a separate container (not a blank since you only have two). Each step requires thorough mixing to ensure an even distribution of cells and accurate results.

The serial dilution process is crucial for obtaining counts within a range conducive to accuracy when it comes to microbial cultures. Only 1 ml is used at each dilution step, making calculations easier with the logarithmic scale. Counting of colonies can be done using either the pour plate or spread plate methods after incubation.