Antiseptic Lab Writeup

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Mackenzie Gill September 8, 2011
Honors BiologyBell 2

Bacteria/Antiseptic Lab


Have you ever wondered what really kills bacteria? In honors biology, it is my job to find an accurate anser. In this lab, out objective was to figure out which antiseptic killed the most bacteria.

In this lab, my partner and I were to swab any surface, and test which of our four antiseptics killed the bacteria we grew overnight in a divided petri dish. We separated the petri dish into four labeled quadrants, and placed one test disc containing one of the four antiseptics in each quadrant. In our study, we used Iodine, Hydrogen Peroxide, Water, and Purell Hand Sanitizer.

An antiseptic is a clean substance that inhibits the growth and reproduction of bacteria, whereas an inhibition zone is the region around a test disc where bacterial growth has been prevented. If the antiseptic is effective, then there is a clear inhibition zone. If the antiseptic does not work, then the inhibition zone still contains bacteria.


If the antiseptics were to work effectively on each contaminated quadrant, then should be a clear inhibition zone.

In this experiment, the controlled group was nonexistent. If we had left one quadrant clear of any antiseptic, we could have a controlled group because we were not manipulating that single quadrant. Although, it is debatable that the water could be a control group, because it is not a chemically inclined substance. Since water is completely clear, people believe it would not kill bacteria.

There were multiple control variables in this experiment. The first was the agar, because all agar is made out of the same materials. Another was the inoculating loop, which we all used for the same purpose, and sterilized the same way. The temperature of the incubator, the incubator itself, and the amount of time...
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