antimicrobial research series

Spring Exhibitions: Focus on Microbes

For spring Exhibitions, students showed a range of projects, including Division III's SHEWASSA (or Simple Human Experiment with a Sound Statistical Analysis), Division II's Ferdinand work, and Division IV's Ethnography Project. In Division I MST, students showed their original antimicrobial research in several formats: oral presentations, journal articles, and blog posts. Below, read a blog post by Division I student Jesse about her group's process and findings:

Antimicrobial Research Series: What Bacteria Does Soap Kill?
Have you ever wondered exactly how well handsoap actually works? We did an experiment to find out how much bacteria softsoap really kills.

Our motivating question was: How much bacteria from a lunch table, the inside of a microwave, a keyboard, and a toilet handle does softsoap kill?

We swabbed each of the areas, and rubbed it all over a petri dish. The petri dishes were split into two halves: one was the experimental side, and one positive control. On the experimental side, we took a mixture of two parts soap and one part water, and swabbed it on top of the bacteria. On the control side, we swabbed water over the bacteria. We also had one more pertri dish. This one was for negative controls. We had one negative control that just had water on it, and one that had the soap mixture on it. Positive controls were a key part of our experiment. Without them, we wouldn’t have known how much bacteria there was to begin with on the experimental petri dishes, so we wouldn’t have have known how much bacteria the soap actually killed. We also used negative controls, which tell you if the water or in our case soap mixture already had bacteria in it. This is helpful if you have bacteria on the experimental petri dishes, because you can say that it came from the water, not the place you swabbed.

What we finally found from our third round of doing the experiment was that the soap works very well. There was no bacteria on the experimental sides of the petri dishes, and the positive controls were covered in bacteria. (as you can see in the pictures below)

It’s not as easy as it seems to answer this question. In our first experiment, we didn’t have any softsoap, so we used Gojo soap and we were not sanitary about putting it into the petri dishes. There also wasn’t much bacteria at all on our positive controls, so we couldn’t say much about what we found. We tried the experiment again and swabbed longer parts of the areas, and got better results, but they were still not perfect. This was because we decided that because there was soap on top of the experimental bacteria, and nothing on top of the positive control, the fact that there was almost no bacteria in the experimental could have been because the bacteria was being smothered by the soap. To solve this, we put a layer of water over the positive controls. This didn’t affect our results, so we are sure now that the bacteria weren’t just being smothered and our results meant something. Lastly, on the third round, there was bacteria on our negative control, but we decided that our negative control was not very important, given our results, so we let it go. Because there was no bacteria on the experimental side, it showed that even if there was bacteria in the water, the soap killed it.

The experimenters all agreed that the most frustrating thing about this experiment was having to redo the experiment multiple times and not getting conclusive results.

Isabel, one of the experimenters, said that “after doing this experiment, I would like to do another experiment to see if there are types of bacteria that this soap can’t kill.”

Antimicrobial Research Series: Oxi-clean v.s. Trader Joe's

By Division I student Ibrahim

You have all heard the catchphrase: “Oxi-Clean, It gets the tough stains out.” You have probably also heard about Trader Joe’s detergent. Both companies have advertised that their product is the best at getting rid of bacteria. But which one is better?

This question is exactly what prompted an experiment designed by Meridian Academy scientists Grace, Kory, and Ibrahim. Their motivating question was “Does Oxiclean or Trader-Joes get rid of bacteria from compost better than the other?”

The difficulties of answering their microbiology project was that they didn’t always have the same type of detergent format. Sometimes they had powder detergent, and other times they had liquid detergent.

Before even starting the experiment, the group hypothesized that Oxiclean would work better in getting rid of bacteria because it is a more renowned brand that focuses mostly on laundry detergent, while Trader-Joe’s isn’t as known, and it develops many things so less time and money might have been put in the detergent, thus resulting in a lesser ability of getting rid of bacteria. After this, they thought of two detergents that they had in their homes that they could use. After choosing Oxiclean and Trader-Joes, the group chose compost as their source of bacteria, because Grace had a lot of it, and so it was convenient.

During the first trial, Grace brought in some compost, powder Oxiclean, and Trader-Joe's detergent. In this experiment, the group had two controls: a positive control and a negative control. A positive control is when you know that there is bacteria. A negative control is when you know that their is no bacteria. The positive control was just compost that they got with a sterile swab. The negative control was one milliliter of detergent with two milliliters of water. They did this for both of the detergents. Then they had Trader Joe’s with water with bacteria, and Oxiclean and water with bacteria. The results were pretty surprising. The Oxiclean negative control looked like bubbly specks. The bacteria had spread everywhere in the bacteria with Oxiclean petri dish. However in the Trader Joe’s with bacteria petri dish, there was a similar result. This would suggest that both detergents were susceptible to bacteria growth. The group thought that the water had increased the ability for bacteria to grow, not exactly the detergent.

The difficulties of analyzing the results was that they didn’t always have the same type of detergent format. Sometimes they had powder detergent, and other times they had liquid detergent.

Soon after trial one, the group did another trial. This time, however, they didn’t do controls because they wanted to do trials only. This time, they used three grams of Oxiclean with bacteria in two of the petri dishes, and three grams of Trader Joe's in the other two petri dishes with bacteria. The results were that The Oxiclean petri dishes were full of bubbly specks and there was no visible bacteria. They hypothesized that the Oxiclean powder dissolved and mixed with the gel at the bottom to create the specks. In the Trader-Joe’s petri dish, there were specks of bacteria visible.

After a long delay, the petri dishes for the third trial arrived. This time the group had 7 dishes so they did 4 controls in order to make up for last time. There was one positive control that was just bacteria. There were 3 negative controls that were Oxi-clean liquid, Oxiclean powder, and Trader-Joe's. Out of the three remaining petri dishes, two were Oxiclean and one was Trader Joe's. There was an oxiclean liquid with bacteria and and an Oxiclean powder with bacteria. The 7th and last petri dish was Trader-Joe's liquid detergent with bacteria. The results of this trial for the Oxiclean was that it worked really well and their wasn’t any real visible bacteria in both the liquid and powder petri dish. There were still bubbly specks in both, but he group had by now come to the conclusion that it was not bacteria because it came up even when their wasn’t any bacteria in the petri dish. The reason that the group thought that the Oxiclean worked really well was that the decrease in water used to make the Oxiclean liquid from last time really helped the detergent prevent bacteria growth. The Trader Joe’s had little visible bacteria and the liquid was visible.

In conclusion, the group found out that Oxi-clean worked better in preventing bacteria. However, water in Oxiclean seemed to help bacteria spread and grow. This is The results of the experiment meant that the groups hypothesis was right. However, this would mean that Oxiclean powder by itself worked better than Oxiclean with water, which is what people do when washing clothes.

For future experiments the group decided that more precise measurements of bacterial growth. The group also agreed that more trials were needed with more time for each trial. More time would mean that we could analyze that results better and we could actually get results that could be put out into the world. Researcher Kory says, “ I think that it was interesting and challenging. However, I would’ve have liked more time to conduct the experiment and to analyze our results.” A big question that was spawned from this experiment was how well detergents from other bigger brands get rid of bacteria.

Throughout this experiment, Grace, Ibrahim, and Kory learned about how it is like to be a real scientist conducting experiments. Researcher Grace said, “ The initial process was exciting, but after a while, it gets less exciting because we already kind of knew what detergent was better at getting rid of compost.    


Antimicrobial Research Series: Mold and Spices

By Division I student Phoebe

Tons of mold!  At least that is what Rhys, Phoebe, and Alex looked at with their experiment.  Their question throughout the project was: What spice out of many is the most effective at preventing bread mold from growing?  The spices the experimenters used were turmeric, cilantro, cinnamon, cloves, nutmeg, oregano, onion, garlic, and ginger.  The best spice out of all of them appeared to be cloves.  It had the least amount of mold on where the spot of spice was and right next to it was nutmeg, who had a lot of mold.  Oregano and cilantro both had quite a bit of mold.  Quite different, right?

Things the experimenters could have done better is making sure things are less contaminated and not exposing the petri dishes to air before using them.    Another thing they could have done better was using the right amount because in the first experiment they had used too much spice and not enough mold, or they could have had none at all because no one could not see mold!  The experimenters also decided that they should change from keyboard bacteria to bread mold because the spices were meant to fight back at molds instead of keyboard bacteria.  

    A couple of things that came in their way is that one, their first negative control had gotten contaminated with a huge spot of bacteria on it.  The point of positive and negative controls are so you can see how things  can grow with mold but no spices and just nothing but water itself.  You can see if the spices have an impact on the mold or the spices do nothing.   also see if mold will appear if there is nothing but distilled water.  The last experiment went better.  Less bacteria, almost none, were in the negative control. The control and the positive control had a lot of mold in it.  The others had plenty of bacteria as well for the experimenters had used a little less spice for the mold.  Things they could have done better is making sure things are less contaminated and not exposing the petri dishes to air before using them.    Another thing they could have done better was using the right amount because in the first experiment they had used too much spice and not enough bacteria, or they could have had none at all because  could not see it!  “The project was an excellent learning except. It taught me many things. I came with an open mind, though, I thought that garlic was antibacterial and it was right” (Alex Cooney).  

In the future, the experimenters said that next they would try to figure out what exactly is in the spices that makes them defend themselves against the molds.  They would probably do a chemical test to figure it out.  What they suggest to do to protect your food from mold is to just sprinkle a bit of spice, (preferably cloves), on the food all over.  Thank you for reading about this project, I hope you have a spicy day!


Antimicrobial Research Series: Febreze and Lysol vs. Bacteria

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!



Antimicrobial Research Series: The Power of Mouthwash

By Division I student Elliot

Do you ever wonder what mouthwash actually does other then making conversations with you more enjoyable? Luca, Theo, and I wanted to know the answer to this question.

Elliot Picture.png

At the end of April our class was split up into groups, each group came up with a different question that they were to answer with provided tools. Our group used 5 petri dishes, one positive control, one negative control, and three petri dishes with bacteria and different amounts of mouthwash. Our positive control was bacteria collected from the back of my mouth with a q-tip, and the negative control was just mouthwash spread on a petri dish.The negative and positive controls are important to see if the mouthwash was actually making a difference in the petri dishes compared to the positive control. The other three petri dishes were spread with bacteria from my mouth and then applied to the petri dishes with different amounts of mouthwash. We spread one with  25%, one with 50%, and 100%, these stood for different amount of drops we put on the dish we would put the certain amount of drops on the dish and swirl it around. I then wrapped the dishes with the sealing tape, so that our results wouldn't be affected by any outside bacteria getting in.

Over the course of a couple weeks we took pictures of the progress of the bacteria. We made sure that we handled the dishes with sterile gloves and with great care, so our results wouldn't be affected.  We had done this project three times, due to contaminated petri dishes previously, we made very strict rules about the handling of the dishes.

“It was interesting to see how different concentrations affected the growth of bacteria,” researcher Theo Cooper said. The 25% and 50% dishes had almost the same amount of bacteria, covering a good ¼ of the dish,  just in different sized colonies, but you can clearly see the difference between 25% and 100%, 100% had much less bacteria, from this result we could conclude that mouthwash does make a difference to the amount of bacteria that forms in your mouth.. The differences between the positive control and the 100% also demonstrated the difference that mouthwash has, even the 25% dish was a large difference from the positive control. In the future I would like to see what difference toothpaste makes to the amount of bacteria on your teeth.

So that mouthwash sitting on your sink should continue to be used, for the sanity of your friends, and for your health.