Week 2

Week 2

Fun With Bacteria: Adventures in the Steubenville Port-a-Potty 

9/3/13

Last Thursday our lab group collected two bacteria samples from a urinal in a local...outhouse. We then incubated the samples in petri dishes over the weekend, so that we could check for signs of bacterial growth in class today. Our samples each grew a thin yellow film, with a few black dots (possibly mold?) near the edges of the dishes. By looking through a microscope, we were able to see the speckled, yellow-green pattern of bacterial growth that our sample produced in greater detail.

Our next task was to isolate a single strain of the bacteria, in hopes of acquiring a pure culture. Using aseptic technique, we sterilized the inoculating loop over our propane torch, waiting until the metal of the loop had turned red before removing it from heat. Once we were confident that the loop was sterile, we swiped the loop over a section of one of our bacteria samples and streaked it across the first quadrant of a new petri dish. We then took turns streaking the bacteria from the sample in the first quadrant across the second, third, and fourth quadrants (and, of course, sterilizing the inoculating loop between each streaking to prevent any contamination). Having prepared this streak plate, we placed it in the incubator at 37' C, and put the original samples into the refrigerator to prevent further growth. By Thursday's class, we hope to find isolated colonies of bacteria on the incubated streak plate, which we can then analyze as a pure bacterial culture.

Week 2

Fun With Bacteria: The Adventure Continues

9/5/13

After incubating our streak plate for two days, we started Thursday's class by looking for an isolated colony of bacteria that we could use as our pure culture. While most of our plate was covered with the same yellowish film we had last week, we also discovered a small group of dots growing on our streak plate. These "dots" of bacteria, since they grew separately from the rest of the plate, were actually pure bacterial colonies that could be used to continue with the rest of the experiment.