How do we dilute a bacterial culture 50-fold, 100-fold, and 200-fold?
You could do the dilutions in one step, or you might have to do serial dilutions.
There is a limit to how much you can dilute a sample in one step.
You probably wouldn't want to dilute by more than a factor of 100 in a single step, because that would give you a large volume of dilute solution.
Rather, you would use the serial dilution technique.
Remember the formula for dilution factor (
Here we can do a single dilution.
We can add 0.2 mL of sample to 9.8 mL of diluent (normal saline? cells will burst in distilled water because of osmotic pressure).
Here, too, we can do a single dilution.
This time we add 0.1 mL of sample to 9.9 mL of saline.
Here you might want to do a serial dilution.
The formula for serial dilutions is
How about a 1:100 dilution followed by a 1:2 dilution?
(1) Add 0.1 mL of sample to 9.9 mL of diluent.
#"DF"_1 = 100#. Call this "Solution 1".
(2) Add 5 mL of Solution 1 to 5 mL of saline. Call this "Solution 2".