Well it appears to have been another successful week of biofilm tests.

This week, I finally moved on from using e.coli to a relatively harmless strain of bacteria called staph.epidermidis. Epidermidis was used in place of a more virulent bacterium, staph.aureus, due to issues of safety and restrictions with having a minor work in a college lab, but luckily, it all worked out. It turns out that BOTH strains of bacteria can be considered gut flora, although epidermidis usually hangs out around the mouth area instead of the lower intestine. So it’s decently representative.

I did the same biofilm tests with the epidermidis as with e.coli over the last few weeks—same procedure, same test tubes, just no bleach. And it seems to have worked. The plate counts showed that there was a 0.5-log reduction of bacteria for BOTH 0.1 mg/mL detergents instead of just one. It’s interesting to see how after diluting the detergents 100 times, they still have a pretty big impact on the bacteria. It’s also interesting that both detergents can have the same effect on different strains of bacteria, especially because e.coli Is gram-negative and staph.epidermidis is gram-positive. (If you want to know the difference between gram-negative and gram-positive, click here: http://www.majordifferences.com/2013/10/difference-gram-positive-vs-gram_2.html#.Vv2CkjE73LJ

The epidermidis biofilm plates

After plating the detergents, I found that there was significant growth with both kinds of detergent, yet another piece of evidence to show that the dish detergents are sweeping biofilms away that would freely grow elsewhere. And here are the graphs!

detergent plates

Overall, these results support my and Dr.Koppisch’s hypothesis that the dish detergents sweep away biofilms instead of killing them. I can’t make any big statements about it yet, but I may be getting closer to understanding the relation of this experiment to the “hygiene hypothesis,” or, in short, the theory that our cleaning products make us more susceptible to illness. In terms of challenges, well, the only real challenge I can think of is remembering to complete all the steps. But overall, things are pretty smooth.

До скорого! (See ya!)

Mackenzie