Mystery TSA Plate by Jessica Ufland

Hello, everyone!

First, I just want to say that the whole idea of this experiment was terrifying to me. I am definitely someone who likes things to be clean, and while I know that the whole world is absolutely covered in microbes, I prefer to not think about it to avoid the whole "ick factor". My dread for this assignment was not assuaged as my mother shared her story about finding staph bacteria on their school drinking fountain when she had done this experiment in school as I was getting ready to head to class. Thanks mom.

I really didn't have any preconceived notions about whether anything I swabbed would be more or less covered in bacteria as I started, but looking back I noticed that I swabbed three things that people come into contact with on a regular basis, and then an actual person. For this experiment, I decided to swab the following four items: 1. my personal lab notebook cover, 2. my microscope handle (which is microscope #6), 3. the space underneath my mother's ring that I wear everyday(just to clarify it is not my own personal mother's ring; my grandmother passed away many years ago, and my mother saved her mother's ring for me after she passed as we were very close), and finally, 4. our classmate Yasmin's cheek. I should note here that I'm very grateful that Yasmin let me swab her cheek as I was too terrified to swab my own.

Unfortunately, I completely forgot to snap a photo of my plates before they went into the incubator so I don't have a starting snapshot of my plates. I did however get the following snapshot of my plates in class on Wednesday, April 6th:

Mystery TSA Plates after approx. 48 hours of incubation

Mystery TSA Plate stored at 24 degrees Celsius after approx. 48 hours of incubation

Mystery TSA Plate stored at 37 degrees Celsius after approx. 48 hours of incubation

As you can see in these photographs, the plates showed very little growth after 48 hours of incubation, especially at 24 degrees Celsius. Being slightly paranoid I had expected to see a myriad of growth, but surprisingly, and joyfully for me, there wasn't much. Starting in the upper right hand corner my lab notebook cover had turned up nothing on the 24 degree Celsius plate, and the 37 degree Celsius plate only had one tiny little white dot. Moving to the upper left hand corner, my microscope handle had also turned up nothing at 24 degrees Celsius, and again had only one dot on the 37 degree Celsius plate, although this time it was much larger than the one seen for my lab notebook. I was still relieved, as I had expected it to be horrifying given how many people use these microscopes on a regular basis, not to mention the things that these microscopes have looked at. Moving down to the bottom right corner, underneath my mother's ring was still a dud at 24 degrees, but grew 5 tiny colonies at 37 degrees Celsius. I hadn't been sure what to expect with this one. Hands are gross given that they touch everything, but at the same time I have to sanitize my hands frequently at work, and my ring does curve upwards so I wasn't sure how much skin contact there really would be on a consistent basis. Finally, in the bottom left corner is the swab I took from Yasmin's cheek. It was the only swab which grew anything at 24 degrees Celsius, with only two tiny colonies, but had the most growth again at 37 degrees Celsius with about 22 colonies growing. This was a surprising find to me. I had expected to see more growth on a person than on non-organic surfaces, but I hadn't expected to see such a large discrepancy.

I had to check my plates after one week and two days as I was absent on Monday, April 11th due to a nasty allergic reaction, but I was able to get my photos on Wednesday, April 13th. Here are the results:

Mystery TSA Plates after one week incubation

Mystery TSA Plate incubated at 24 degrees Celsius after one week of incubation

Mystery TSA Plate Incubated at 37 degrees Celsius after one week of incubation

In looking at my plates after one week of incubation there really wasn't too much change on my plate which was incubated at 24 degrees Celsius. There was still no growth for either my lab notebook or my microscope handle (Sections #1 and #2), but section #3, underneath my mother's ring, did show some growth with about 4 small colonies. Section #4, Yasmin's cheek, had a substantial amount of growth as far as size, but only had 25 colonies which is not much larger than the 22 counted after 48 hours of incubation. The 37 degree Celsius plate was another story. This was the plate that I had been afraid to see, although truth be told, it could have been so much worse. Section #1, my lab notebook, had only one colony, as did my microscope handle in section #2 which I had thought was going to have significantly more colonies growing on my plate. Section #3, under my mother's ring, had only 6 colonies growing which was also surprisingly low. Section #4, which was swabbed from Yasmin's cheek, was another story. This was the section of the plate with by far the most growth, with approximately 70 colonies, although many of the colonies were very close to each other making counting very difficult so there may be some more or less than this estimate.

Due to limited time, I was unable to look at anything under the dissecting microscope which makes any kind of identification slightly more difficult.Many of the colonies do not appear to be raised, but given that I could not look at them under a dissecting microscope it makes this difficult to identify. Some of the white, circular colonies may be Staphylococcus aureus, but under another site these colonies were listed as being yellow as well so it is still difficult to say. I haven't been able to find anything that may be orange as the ones that are seen in section #4. They may be Serratia marcenscens, but again I'm not entirely sure. I would love to hear from anyone who has thoughts as to what this is, and may have discovered the same thing!

Sources:
http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_Interpreting_Plates.shtml

http://www.microbelibrary.org/component/resource/laboratory-test/3114-colony-morphology?limit=0&limitstart=0