Blog Post #3: Mystery-Microbes

• What objects did you decide to sample and why?

I chose to sample my phone (section 1), the door to the lab (section 2), the door that leads to the lab corridor (section 4), and the inside of the bathroom door (section 3). I chose my phone because I was curious about how contaminated my phone surface was, as I typically use my phone regularly. I tested the bathroom door to see if people washed their hands after using it and I wanted to test the lab door handle to see if people sanitized prior to conducting experiments in lab. The corridor door handle was tested because it experiences higher foot traffic, so I thought it would more likely be contaminated.

Figure 1: My Petri dish on Day 3 with very little microbial growth.

Figure 2: My Petri dish on Day 7 with more microbial growth.

·        What type of growth did you see on Day 3? On Day 7? Describe the growth.

On day 3 I did not see much growth from any of my samples. On Day 7 I observed colonies on the bathroom door handle sample, as well as the lab door handle sample. I did not observe any growth on my phone sample, nor the corridor door handle sample.

·        Did you have growth from all the samples? If not, why do you think that happened?

I did not have growth from all my samples as I alluded to above. Just because I did not see growth on the petri dish for those samples does not mean that microbes were not present on those sample surfaces. We can only grow about 1% of bacteria in lab and the TSA (tryptic soy agar) we used as the carbon source for this lab promotes microbes that need access to vitamins and proteins(found in soy products) versus GSA (glucose salt agar) which promotes bacteria that can make cell components from glucose.

·        What sample yielded the most growth of organisms? Why do you think that happened?

The Bathroom door handle sample yielded the most colony growth. This is contributed to the environment, human hands are exposed to a plethora of microbes while coming in close contact to human waste products, this is why many people generally wash their hands after using the bathroom to reduce illness, this test proves that not everyone washes their hands, which can readily be observed.

Figure 3: Reddish-brown colony on the plate section from the lab door handle. 

·         Did anything about the growth you observed surprise you?

I wasn’t surprised by the growth I observed as it was in the samples nature to be prone to contamination, however, the growth on the lab’s door handle was reddish-brown, while the growth on the bathroom door was beige. I was surprised by the lack of growth on my phone surface, many others in lab saw microbe growth on their phone samples. I am adamant when it comes to washing my hands after touching surfaces I expect to be contaminated. While I didn’t see any growth from my phone sample this does not mean microbes are not present.

Figure 4: Michelle's Petri Dish on Day 7.

·        Describe the plate of your lab mate. What did you notice about their plate?

I compared my plate with Michelle’s, she tested her phone surface, the lab desk, the door knob, and the sink. She saw more growth on the door handle and the desk, a little growth on her phone surface, and no growth on the sink sample. I noticed that she saw microbe growth on her phone sample, where I did not.

·        Compare and contrast your plate with your lab mate's plate.

Our results agree in regard to the door handle having contamination by microbes. While she saw some growth on her phone it was not as much as one would expect from a phone surface, as a phone is something most of us are in contact with throughout the day. She saw more growth on her sample of the lab’s door knob, this could be contributed to by the fact she took the sample from within the lab, and I took my sample from outside the lab.

·        Reflection: What does this mini experiment reveal to you about the ubiquity of microorganisms?

Microorganisms can live in a wide range of places and can even survive for periods of time in a dormant state, further expanding the range of objects they can be found on. Although I did not see microbial growth in all my samples, microorganisms are rather ubiquitous and grow well in areas that many other organisms cannot, due to their quick generation time, dormancy, and prevalence in the environment, microorganisms can be found almost anywhere.  Like most things in life, however, they do better in certain conditions than other; for example, bacteria that grows well in damp soil would not do as well in dry soil conditions, so in that way they are somewhat limited (specialized).

·         Write at least 3 scientific questions based on your observation.

1.     Would I obtain microbial growth from my phone in a different medium?

2.     Why was there a difference in color between colonies growing on the same type of surface?

3.     Was there a correlation between the lab’s corridor door handle sample, hosting no growth, and the higher foot traffic it experiences?

Hypothesis: If a surface experiences different conditions (light and temperature), different variants of microbes will be present.