On the 25th and 27th of October, our AP Bio class had the opportunity to meet Professor John Stavrinedes, a microbiology professor and did a bacterial isolation lab at the University of Regina.
DAY 1: (10-25-17)
As part of our lab experiment, 5 swabs were given as well as 4 agar plates. We were then instructed to swab five different surfaces around the cafeteria, dipping the swabs into the tube of water that was also given before swabbing in order to have a higher chance of getting the most of bacteria from a certain surface.
I particularly sampled several surfaces such as the inside door handle and bench, the soil, a leaf and the outer layer of my shoes.
Our next step was to label our plates before gently streaking the swabs into our petri dishes that contained different agars. I purposely spread all of my five samples on all three plates in the sense that I would be able to observe different types of bacteria. All four plates were tightly sealed and incubated for almost 24 hours, allowing the bacteria to grow.
Day 2: (10-27-17) THE RESULTS!
Excited about the results, I noticed that my door handle bacteria sample appeared colourless on the Brilliant Green Bile, appeared pink on the MacConkey plate and more than 20 colonies were shown on the LB plate. Obviously, these plates have different purposes. The MacConkey is selective for gram-negative bacteria while the Lysogeny Broth plate is used for the growth of bacteria. Brilliant green bile inhibits
gram-positive bacteria and most gram-negative bacteria.
We also had the chance to observe each other’s plates. The results were diverse! From my observation, some plates showed less to no growth at all while other plates showed a significant amount of growth. Why is this?
Some reasons may include:
- We only took a small sample from a specific spot or swabbed lightly on the surface
- The surfaces that we took samples from could’ve been cleaned recently.
- 99% OF BACTERIA CAN NOT BE CULTURED. What we saw on the plates is just the 1% that survived the temperature during the incubation.
Gram-positive and Gram-negative
What interested me the most throughout this experience was the Gram-positive and Gram-negative bacteria.
A Gram-positive bacteria retains the color of the crystal violet stain in the Gram stain because of its thick peptidoglycan cell wall while a Gram-negative bacteria will stain red because its thin peptidoglycan layer surrounded by the plasma membrane.
During the discussion, we were asked to determine which part from a typical household contains the most bacteria. Majority of the class suggested that it was the toilet seat but whether you believe it or not, the sponge contains the most bacteria. Does that mean that dishwasher soaps are not reliable in killing bacteria?
Enjoy the little things… like bacteria!
People live in fear of bacteria. One would argue that bacteria are harmful but the right bacteria in the right place can be beneficial. An example would be the mighty Lactobacillus casei , a type of bacteria that is naturally found in our gut, as well as in fermented foods such as yogurt. L. Casie supports organ health, has allergy benefits, digestive benefits and many more! Good health begins in the gut. A study also suggested that being exposed to bacteria is a step in developing a healthy immune system but don’t just rely on them because wrong bacteria in the wrong place can cause problems. Vaccinations and proper hygiene are necessary.
This AP Bio trip at the UofR was a very exciting experience. Performing a lab with a university professor and having an opportunity to get a hands-on experience with science rather than just talking about it in class was more enjoyable.