Mystery TSA Plates by Shane Hall

Figure 1 – TSA plates before experimentation.

                   

Day 0:

     As seen in Figure 1 above, I divided my plates into four sections for measuring bacterial growth.  Two sections of each plate contained samples from two of my body parts, my arm and my leg.  A third section had a sample taken from the backside of my cell phone and the fourth had a sample where I borrowed some of Emma’s expired lemon juice to study.  Of course, no growth was observed at that time.  Each plate was then incubated at specific temperatures; the plate on the left in Figure 1 was placed at room temperature while the one on the right was incubated at 37 degrees Celsius.  For this experiment, I hypothesized that the lemon juice would produce no growth due to the acidity of the substance and, therefore, its bleak potential for bacterial growth.  I theorized that more growth would occur on the TSA plate kept at room temperature due to the habitat of the bacteria and its possible limited growth.  As for the other sections, I expected to see a decent amount of bacterial growth especially for the cell phone section since I have placed my cell phone on multiple random surfaces without necessarily cleaning the device.

Figure 2- TSA plates after two days of experimentation.

                                      

Day 2:

     After two days of incubation, I was surprised to see hardly any bacterial growth.  As shown above in Figure 2, the TSA plate kept at room temperature is now on the right while the plate incubated at 37 degrees Celsius is on the left.  The only bacteria I observed on the plates was from one small bacterial growth from my arm on the plate kept at 37 degrees Celsius.  I expected this of the lemon juice sample, but I originally thought there would be at least some bacteria on my phone and body sections.  Perhaps the areas were not properly swabbed or the samples not correctly applied to the TSA plates in a manner that would encourage growth.  Of course, there is the possibility that there was not much bacteria to culture from the selected areas.  At least the TSA plate produced slight growth for the sample taken from my arm and I expect it to flourish by the next time my plates are observed.

Figure 3 – TSA plates after seven days of experimentation.

                             

Day 7:

     Miraculously, growth was observed on both plates by the seventh day.  Unfortunately, I did not anticipate where the bacteria would grow all that well.  Observing Figure 3, we see that my room temperature TSA plate has now returned to the left side while my plate incubated at 37 degrees Celsius is back on the right side.  The arm section on my body temperature plate did grow since the last time I saw the bacteria.  It has now become a small bacterial colony since then.  What truly surprised me is the fact the Figure 3 shows that I have received the most growth from lemon juice on both of my plates.  The bacteria appeared to grow more so at room temperature, producing a large colony.  I would almost go so far as to call the bacteria a lawn of growth as opposed to the plate incubated at body temperature which grew to be a mid-sized colony.  In any case, the growth shocked me by far.  

     Despite my hypothesis being incorrect, I was intrigued by the growth and decided to place it underneath a compound microscope to view the bacteria that was cultured.  I did not have a chance to gather any images from the dissecting microscope, unfortunately.  The two photographs below show the bacteria in greater detail (Figure 4 and Figure 5).  The figure on the left (40x magnification) shows a portion of the sample as a whole while the figure on the right (100x magnification) shows the same sample up close and personal.  Figure 6, as seen below, shows a different area of the same sample (100x magnification).  While my arm’s bacteria might be a type of Staphylococcus, I am having trouble identifying the lemon juice bacteria.  Perhaps it is another form of Staphylococcus as well.      

Figure 4 – Lemon juice bacteria at 40x 

magnification.

Figure 5 – Lemon juice bacteria at 100x 

magnification.

                         
                                                             

Figure 6 – Lemon juice bacteria at 100x magnification.

     As seen in the previous photos, bacteria growth is possible on lemon juice.  Though, this is indeed curious as there are several home remedies and methods for killing bacteria using substances such as lemon juice due to its high acidity.  Perhaps the fact that the lemon juice expired somehow changed the composition of the substance and allowed a nice breeding ground for bacteria to thrive.  I also noticed that there was more growth on the room temperature sample than the body temperature sample, signaling me that the bacteria present does not survive at high temperatures and supporting at least one part of my original hypothesis.  Only one other person in my group was able to culture bacteria from their lemon juice, so the inconsistency of our results does not seem to support my hypothesis either.  

     However, I did expect bacterial growth for the sections containing my arm’s bacteria.  Granted the growth was small, it was still present.  Although, no growth was seen on the cell phone or leg sections of my TSA plates.  At this point, I suspect that I am either incredibly good at keeping bacteria off of me and my belongings, or there was some type of application error with the culture swabs.  I found that the sources for collecting bacteria are limitless, however.  This information I have acquired is enough for me to believe that bacteria can truly grow anywhere if the conditions are just right.