November 15th, 2011
Today I did an experiment to see the effect of UV light on bacteria. I inoculated my bacteria on a starch plate and divided it in half by drawing a line. I took the lid off and put a piece of paper on one half while exposing the other half to UV light for 30 seconds. I then incubated the plate to see how it will grow now. The class observed a SteriPen experiment to see how much bacteria can be reduced by it. First bacteria were added to a beaker of water and then some of the infected water was poured into a control Petri dish. Then the SteriPen was used on the water for about a minute before some of the water was poured into another Petri dish. The two dishes were incubated to see how much bacteria grows in each. Another class experiment was making yogurt with and without Kefir. The milk was heated to a certain temperature and then the Kefir was added to one while pre-made yogurt was added to another. Then they were put away to ferment.
November 17th, 2011
When I checked the UV light-treated plate, the side that the UV light affected had very little bacteria growing in it. If the UV light was used longer than it had, the bacteria on that side would have completely died. The unexposed side was growing just fine. After that the class taste-tested the yogurt made from Kefir and pre-made yogurt. The class preferred the Kefir sample because the Yogurt sample over-fermented and became very sour. The class also examined the plates of the SteriPen experiment. Although some bacteria were growing in the treated sample, there were noticeably more bacteria growing in the control sample.
