First Day! Streak Method, Gram Stain Test and Microscope.
First day in the STEM-TRAIN program. I learned about the “Streak Plate Method”, the “Gram Stain Test” and how to use a microscope. (Sept. 10th, 2019)
V-Fisheri bacteria
At the beginning of the class, Shawn, a senior student, explained to me the experiment he was working on. He was working with V-fisheri bacteria that have as bioluminescent properties. The goal of his experiment is to find some components that can stop the bacteria from releasing AHL molecules.- The V-fischeri bacteria is a gram-negative bacterium found in marine environments
- When it multiplies and it is ready to communicate with each other, it releases QS molecules.
- When these molecules are released, the biofilm glows.
- If the biofilm doesn’t glow there is “something” that stops the communication among these bacteria
Pathogenic bacteria also release molecules when it tries to communicate with the others; however, these molecules are toxins. The V-fisheri experiment is successful, it can be applied to pathogenic bacteria.
I didn't take a picture, but I found one on the National Science Foundation webpage that shows how the bacteria should look when it's under UV light. "Images in this webpage are allowed for educational and non-profit use"
Streak plate method
I learned how to prepare before this experiment some of the lab equipment during the experiment.
- We used the Bunsen burner to sterilize the nozzle of the flask because most of the bacteria die at high temperatures. IMAGE 1A & IMAGE 1B
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| IMAGE 1A |
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| IMAGE 1B |
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| IMAGE 2A |
- The pipette pump is placed in the Mohr Pipette, while the pipette is in the bag. (It avoids cross-contamination) Do not let the pipette touch anything. IMAGE 2A
This is the process to put the broth media (with bacteria colonies) to a petri dish:
- First put some of the broth in a test tube, to avoid contaminating the whole flask.
- Once in the test tube, use a loop to spread the bacteria into the petri dish.
Remember to sterilize the flask before putting it away for storage.
- First, we sterilize the loop with fire and let it cool. IMAGE 2A & IMAGE 2B
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| IMAGE 2A |
- Then, we inserted the loop into the sample, and smear on the edge of the plate. Also, make sure of using the loop in the right way. IMAGE 3A & IMAGE 3B
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| IMAGE 2B |
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| IMAGE 3A |
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| IMAGE 3B |
- We sterilized the loop again and made think strikes from the smear. We repeated these 4 more times. (drawing of the plate and the loop on the surface). That would be STEP 1
- Before every other group of strikes is made: sterilized the loop, let it cool, and then strike thin lines.
- When you're finished, type both sides of the petri dish and incubate it.
Remember to sterilize the loop before putting it away for storage.
Gram Stain Test
This test helps to differentiate between 2 large groups of bacteria
based on cell wall constituent.
The test consists of coloring the peptidoglycan layer of the bacteria.
I will explain this test in another post because we have done it other times, and I didn't take a picture of my bacteria the first time (It was Gram Negative).
Microscope
When I did my first Gram Stain Test, I learned how to use a microscope for the first time. Shon taught me how to look for my bacteria, and how to clean the microscope after using it.
I feel like a video would be better explaining this because once you start using the x10, x40 and x100 lens, you have to be careful. Remember to hold the microscope with both hands!
I know it's a lot. When I started writing this post, I realized that I learned many things in just one day. The most impressive thing is that time flies when we're in the lab.
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