Alas, it's Thursday, nearing the end of week 3 of my bubbly adventure. Luckily, I'm not dying, but hopefully within the next 24 hours, some unfortunate bacteria will. I am sorry to say that I do not yet have the MICs completed quite yet, but they will be done tomorrow. Tomorrow, I will post a short summary of the MIC results as to not leave you hanging, looking at random pictures of agar and well plates. Hopefully, what I have below will suffice. And I'm sorry for the microbiology jargon you will encounter if you read ahead.

Studying bacteria is a slow and tedious process. The bacteria grow best overnight, and between procedures, there is quite a bit of waiting involved. So here's a run-down of what I did this week:
I re-made my bacterial stocks so they would grow better, but the new Lactobacillus stock did not grow. We think there is another type of broth (media) that Lactobacillus best grows in, so we might get our hands on some MRS broth in the near future. I diluted all the new samples and plated them. I streaked an agar plate for Lactobacillus for good measure. Here are what the plates looked like the next day...

The e.coli plate

The Lactobacillus plate- ain't it purdy?

S.epidermidis- better growth!

I then took the OD of each new stock. They were as follows for Lactobacillus, e.coli and s.epidermidis: 2.29, 1.52, 0.9. So why was this important? We used these OD's to calculate the CFU (colony-forming units) per optimum density (OD) at the bacteria's highest growth rate. This number happened to be 0.4. After using a spreadsheet to do calculations, the CFU/ OD 0.4 were calculated using the following equation:

0.4(Avg CFU per mL/ OD measured). This yielded the results:

E.coli= 2.4E7 CFU/ OD 0.4
S.epidermidis= 2.18E7 CFU/OD 0.4
Lactobacillus= 5.24E7 CFU/OD 0.4

This meant that there was a good concentration of bacteria at the optimum growth rate, so we decided to go along and do the MIC. The optimum CFU/OD 0.4 of most bacteria is around 2.5E5. We diluted the e.coli and s. epidermidis samples 20uL/ mL and the Lactobacillus 10 uL/mL in test tubes. Then, I took a 96- well plate and organized it like this:

I started out with 200 uL of dish soap in column 2, then took my pipettes and moved 100 uL down the line, leaving the end row untouched by the detergent. When it was time to add the bacteria, I put 100 uL of diluted bacterial stock in each well.  I did this for all three types of bacteria, and Voila! Three beautiful plates ready to go in the incubator- one for each strain.

Clockwise: E.coli, S.epidermidis, Lactobacillus.

So while I must wait until tomorrow to get usable data, it is nice to finally be getting used to the procedures. I am left unsupervised most of the time, but I think I've done everything basically right. With the greater concentration of dish detergent, hopefully tomorrow we will get some solid data.

Now I wait for my well plates to grow, slowly. While writing this post, I'm eating yogurt, and it's pretty awkward to basically eat what you're studying in the lab, but oh well. I guess gut flora taste delicious.

до завтра (until tomorrow),

Mackenzie