In biology class, students have been studying microbiology, learning about viral and bacterial structures and how each can cause disease, though most kinds of bacteria are harmless to us and many are critical in our own microbiomes or to the environment. As part of this unit, students designed and carried out two experiments with bacteria. In one, bacteria content from two locations in the environment around us were tested, and in the other, agents that inhibit bacteria were compared. Planning the experiments allowed students to revisit the ideas of the scientific method, used recently for their science fair projects. They thought about what comparisons would be interesting and wrote hypotheses. For example, one team compared bacterial presence on a cell phone and on a computer keypad. Another team compared the effectiveness of hand soap, dish soap and hand sanitizer as to their ability to slow bacterial growth.
The experiment gave students the opportunity to learn microbiology methods. They needed to use “sterile technique” to be sure the microbes they were growing were those from the intended sources and not contaminants. The students used Bunsen burners and sterilized bacterial spreaders and forceps. In the experiment on microbial inhibitors, they used two different species of non-pathogenic bacteria to demonstrate that different inhibitors work better on different microbes. One interesting result was that hand sanitizers did not work well on either species of bacteria – it may be that the alcohol in them dissipates when the container has been open for a while. The best inhibitor, by far, for surfaces was bleach. I was very impressed with what a great job all of the students did in this extended lab activity!