Hi guys-

In order to prepare for the biofilm tests that are coming up this week, it is necessary to show you one of the essential aspects of biofilm tests, and quite frankly, working with microbes at all: serial dilutions.

Luckily, serial dilutions are pretty simple.

For the general procedure, I took 6 test tubes for each microbe, filled each with 3mL of autoclaved water, lined the test tubes up in a row, and filled the first with 300 uL of inoculated stock. I put the test tube in a vortexor( it basically spins the test tube to mix stuff and ensure there are no clumps of bacteria floating around that could affect the results). While it is natural for stuff to settle at the bottom of a test tube, if it is not mixed properly, it could alter the concentration, OD, etc. and change results.  Then I  took 300 uL from that first test tube, put it in the next one, and did the same thing. It looks like this:

After that, for all three types of bacteria, I took agar plates, split them up into 6 sections (one for each dilution) and put 15 uL of diluted stock into each section. Then into the incubator they went to grow overnight! If you did it right, it should look like this:

Based on the kind of procedure you're doing with these plates, you can either perform an enumeration(count the plates to ensure the bacteria are growing well) or you could be performing a biofilm test. The biofilm test is different, but I will go over it in the next couple of days.

Well I hope that little nugget of information was helpful. You can generally do this kind of thing with different types of microbes, but at least I hope you are now educated on one of the most important microbiological procedures and that you are ready to hear about the biofilm tests!

увидимся (see you!)

Mackenzie