Mystery TSA Plate by Karina Yu

Day 0:

In this experiment I wanted to see the bacterial growth from four sources. I wanted to see what bacteria grew in my mouth, under my shoe, on my skin (palm), and in a bottle of expired lemon juice. I took a swab of each source and made duplicate dishes, one was stored at 24°C (room temperature) and the other was stored at 37°C (body temperature). I hypothesized that my mouth would grow a good amount of bacteria because it is a moist, warm environment with nutrients coming in from eating food.

Next, I thought that I would have the most variety of bacteria under my shoe because it has been exposed to many areas of the ground where others have walked on. I could have picked up whatever bacteria was under their shoes. I figured if there was variety, than it must have some bacteria that will grow well in both plates.

As for my skin (palm), I believed I would have the most bacterial growth out of all the other sources because throughout the day I had touched door handles, keyboards, tables, etc. All these things that everyone else has had contact with, and probably isn’t washed often.

Lately, the lemon juice. The bottle of lemon juice was brought in by a lab partner. It had expired on September 19, 2015 and had developed a good inch of mold at the bottom.  For this sample wasn’t sure whether any bacteria would grow because of the acidity of the lemon juice.

Day 0 (Left: 24°C, Right: 37°C)

Day 2:

On day two I examined both my plates and there was already a huge amount of growth. In the 24°C plate, there was no growth on my skin (palm) or in lemon juice. However for the mouth, it turned a cloudy white and had tiny faint white dots in the exact shape that I swabbed on my plate. From under my shoe there was already 13 circular yellowish white colonies. In the 37°C plate, the bacterial growth was more significant. The mouth area was the same as in the 24°C plate but more pronounced. The bacteria that was under my shoe had 9 huge colonies, it could almost already be considered a lawn. Note that it has already started to overgrow its boundaries. While the skin (palm) had no growth in the 24°C plate, there were 60 colonies in the 37°C plate. And the lemon juice also had no growth.

Day 2 (Left: 24°C , Right: 37°C)

Day 7:

After incubating for seven days, I was shocked at how much bacteria grew on my plates. In both plates I could no longer accurately count the colonies of the other sources because the bacteria that was under my shoe had absolutely grown over the mouth, lemon juice, and skin (palm) section of the plate. From this cool website with terms for describing bacteria/yeast/mold colonies on media the bacteria under my shoe seem to be a raised, filiform yellowish white lawn. Using the medical microbe gallery my bacteria looked like the Isolation of an Unknown Bacterium on Trypticase Soy Agar.

Day 7 (Left: 24°C , Right: 37°C )