Mystery TSA Dish by Gerar Suaverdez

The goal of the first lab was to observe growth of bacteria by using a cotton swab dipped in sterile water to obtain bacteria from various objects and allow them to grow on a TSA plate. The TSA plate was used as a growth medium that provided enough nutrients for the bacteria to grow. The objects I obtained bacteria from was my phone screen and the arm of a chair that was in the lab. I picked my phone screen because I hypothesized that there would be a lot of bacteria growth because it was an object that was used every day even though it was cleaned often. I was curious about how actually dirty my phone screen was. The arm of a chair was also tested because I thought there would be a lot of bacteria growth since I did not believe that the chairs were not cleaned often and different amounts of people use the chair every day. The TSA plate was duplicated during the experiment and on plate was incubated at room temperature (24 degrees Celsius) and another at 37 degrees Celsius (98.6 degrees Fahrenheit).

The plates were made on April 4th and examined on April 6th and can be seen below.  

                        

These are the bacteria grown on TSA plates, the left being incubated at 37°C and the right at 24°C.The bacteria that grew appeared in small colonies and had a milky, crème color. At 37°C, the phone screen had one small colony and the arm chair had 7 colonies. At room temperature, the arm chair had 7 smaller colonies while the phone screen did not seem to have any growth.

The plates were examined again on April 11 and can be seen below.

                

These are the bacteria grown on TSA plates, the right being incubated at 37°C and the left at 24°C. The bacteria in the arm chair at room temperature grew even larger and seemed to form a lawn while some retained its circular shape. Meanwhile, the bacteria in the arm chair at 37°C had a darker yellow color and some of the bacteria grown had ridged edges instead of a circular, smooth outline. These also seemed to form a lawn when they were close to each other. For the phone screen, there was not that much growth at room temperature; there was only one colony formed. At 37°C, there was only one more colony, but the bacteria had turned a darker yellow color.

Below is a picture of the bacteria from the chair incubated at 37°C, viewed at a magnitude of 400x.

This picture shows that the bacteria that grew on my TSA plate from the arm chair may have actually grew as lawn instead of as colonies because the bacteria are conjoined together and appear as one. 

In conclusion, my hypothesis that there would be a lot of bacteria grown if it was taken from my phone screen was proven incorrect. There was actually a small, surprising amount at room temperature and at 37°C. However, the arm chair did have a lot of bacteria. These findings tell me that my phone screen may be “cleaner” than most of the objects I might come in contact with even though my phone screen is touched every day. These findings also tell me that a temperature of 37°C is more optimal for growth of bacteria than growing the bacteria at room temperature. 37°C is actually the temperature of the human body and is the ideal temperature for studying human pathogens. This is quite scary because these are the things that can potentially grow inside one’s body if a person does not take care of their hygiene. I think this experiment assures others that they should wash their hands regularly because you can come in contact with bacteria from places you might not even expect.