By Division I student Lila
Have you ever wondered if febreze can clean your room at the same time it is making it smell better? Well, it can! Over the course of the last few months, Vilmarie, Zayna, and Lila have been testing out whether febreze or lysol can kill or stop the growth of bacteria. The question was, does febreze air freshener stop the growth of bacteria from the P.E. room left pull-up bar? This area was chosen because lots of people use it and spread bacteria all over it. So, it would be a good place to collect bacteria for the experiment.
The protocol was to swab the left pull-up bar in the P.E. room with distilled water and rub onto petri dish. There would then be a reservoir of febreze that connects into the petri dish through a absorbent strip of paper. They would then have another petri dish that was split in half and marked one half as positive control, just the pull-up bar bacteria, and negative control, just distilled water. With these controls, they can compare the end results with the plain water or bacteria. For an example, if the water had bacteria in it to begin with, they would know that that contributed to the result.
When they finished this experiment, they found that there was bacteria growing, but not only on the positive control. It was growing on the negative control too! This was a confusing result: how had the bacteria gotten into the negative side? They later figured out that since the two controls were sharing a petri dish, the positive spread into the negative one. Also, there was still bacteria growing on the petri dish with the reservoir of febreze, which did not match up with their hypothesis. So, as you might have guessed, the protocol needed a little tweaking.
Their next experiment was a little different. Since the last experiment did not do so well with the controls, they had the idea of having two separate petri dishes for each control. This would hopefully clear up the spreading of bacteria in the dish problem. And it did! Both controls turned out as expected, the positive with bacteria and the negative without bacteria. However, they still wanted to try to prove that febreze can kill bacteria. So, they tried a new method instead of the reservoir. Spraying the febreze straight from the can, they continuously sprayed the petri dish for 10 seconds. This created a little pool of febreze in the bottom of the dish. After 5 minutes, they poured out the liquid, thinking that it had created a sort of layer or coat on the agar. However, they soon realized that they might have washed away all of the bacteria because there was so much liquid in the petri dish. The dish that was labeled febreze had no bacteria, another sign of the bacteria maybe being washed away. And yet again, they needed a change to even more perfect their experiment.
This time, they took a lot of things into consideration. They didn’t want to repeat any prior mistakes again. So, they tried just pouring a little febreze over the bacteria in the petri dish. They decided to pour 1 millimeter of febreze over the agar, and to be fair and even with the other dishes, they poured the same amount of distilled water over the two controls so that each had a small layer of liquid in the bottom of their petri dish. And, they also decided to make a control for the febreze to show if the febreze by itself had any bacteria in it. However, it turned out that it didn’t. The febreze petri dish ended up with no bacteria in it, but they decided to count the number of bacteria that had grown in the positive control. If they counted them by hand every single day, that would be a lot of work. Thankfully, they didn't have to do that. They set up a method where there was graph paper under the petri dish, and they counted the number of graph squares there were in total that fit in the circle under the petri dish. It came out to be 150 squares. Then, looking down onto the petri dish from above, they would count how many squares the bacteria could fill up:
“This project has taught me how to work better as a team, [learn] about different microbes and their growth, while at the same time it was a fun and engaging project!” says Zayna after having a conversation about the experiments with Lila. To look deeper into the process, there will be a lab report and presentation that will be at exhibitions for everyone to see!