Mystery TSA Plates by Kateka Seth

For this experiment, I chose to test for bacteria in places in most commonly touch around lab. The four places I chose are as follow:

1. Sink Handle
2. Lab Table Surface
3. Door Handle
4. My mouth (Note: I don't commonly touch my mouth around lab. This was for curiosity's sake, I swear.)

Day 0:

Not much to see on the day 0 plates besides my bad decision of not straightening out the plate (this picture really brings out my OCD). My prediction in terms of bacteria growth was that door handles would have the most followed by sink, then table, and lastly mouth. I would hope that my mouth would have less bacteria than these 3 surfaces. 

Day 2: 

My predictions were completely thrashed. I had expected that the bacteria plate held at 37 degree C would grow more than the one at 24 degree, but all other predictions were off. Bacteria would grow more at 37 degree because it is a warmer temperature, and most likely a more hospitable one for some. 37 degree C is human body temperature while 24 degree is room temperature. This means that bacteria more readily grow on us than inanimate objects around the room. Not the nicest thought, but it should be remembered that bacteria does not equal dirty. Without bacteria on our bodies we would not be able to function correctly. 

Colony count for Day 2:

	24 Degree	37 Degree
Sink Handle	11	A lot (20-25)
Lab Table Surface	None	1
Door Handle	None	None
Mouth	None	Tiny colonies (uncountable)

It was interesting to note that the door handle had no bacteria growth on either plate, which is completely different from my predictions. The growth of sink handle bacteria was insane, and quite frankly gross. Although unexpected to me, this growth was not unprecedented as people's hands are their dirtiest when they go to wash them. My mouth also had bacteria growth, but only on the 37 degree plate. This could possibly mean that the bacteria is native to the habitat of my mouth, and wouldn't survive in a different temperature environment. 

Day 7:

Day 7 brought about even more bacteria growth. The mouth bacteria on the 24 degree plate started to grow, and I can assume that these bacteria can survive in an environment different from my mouth. The sink handle on the 37 degree plate became even grosser with the new bacteria growth. The mouth bacteria also grew in size as the dots are much more noticeable than they were in day 2. If you didn't have a reason to brush your teeth before, let this be one. 

Colony count for Day 7: 

	24 Degree	37 Degree
Sink Handle	16	A lot (lawn-type growth)
Lab Table Surface	None	1
Door Handle	None	None
Mouth	Tiny colonies. One big	Many tiny colonies

The colony count did not change drastically from day 2. Mostly, the existing colonies simply got bigger and fused together. I was surprised that the door handle still did not show any sign of bacteria growth. Door handles tend to get a lot of hate, but this mystery TSA plate experiment has shown that they really don't deserve that hate. They're quite clean compared to the other surfaces we touch on a daily basis. 

Identification: 

To help me identify the bacteria grown on my plates, I used this gallery as well as the two links provided in Gwen's post.

Fig 1. Sink handle at 37 C. Day 7

Fig 2. Sink handle at 24 C. Day 7

The sink handle bacteria growth was relatively easy to identify. Both images show growth of some sort of unknown fungus, according to this site. Fig 1 shows a colony that takes a very particular shape, but unfortunately I was not able to identify it. The closest image to it from the previously mentioned site simply says "unknown isolate morphology."

Fig 3. Mouth at 37 C. Day 7

I really wanted to be able to identify these bacteria since they take up residence in my mouth, but I couldn't find one straight answer. Their round shape does not eliminate many bacteria. The most interesting feature is that each circle has another dot inside which looks like a nucleus. I was hoping this feature would allow me to identify it, but none of the gallery pictures have a bacteria which show a clear nucleus like this. I thought the closest match to be Staphylococcus aureus or Corynebacterium xerosis. I am interested in what you guys think it might be, or if any of your bacteria had the same nucleus-like feature as mine. Staph. aureus isn't uncommon to have on your body, but it could cause infection, so I'm hoping this bacteria is not aureus. I don't know much about Corynebacterium xerosis, but a quick google search leads me to believe that it is relatively innocuous.

This experiment provided me with a new perspective on the surfaces we touch everyday. Unfortunately, I'm not so sure I enjoy this new POV.