Week 3 labster PDF

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labster for week 3...

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BIOS242, Week 3-OL Name:

Lab 3: The Gram Stain: Identify and differentiate bacteria Learning Outcomes    

Describe the structure of the Gram-positive and Gram-negative bacteria. Identify theoretical and technical aspects of the Gram staining procedure. Identify the most commonly made mistakes in Gram staining. Analyze the results of a Gram staining experiment using a light microscope.

About the Gram Stain: Identify and differentiate bacteria Virtual Simulation Lab Did you know that there are approximately 5 million-trillion-trillion bacteria in the world? Most of them are harmless, but some can induce disease in an affected host. In this simulation, you will help doctors identify bacteria in a cerebrospinal fluid sample from a patient suspected of suffering from bacterial meningitis. Explore the bacterial cell wall Compare and contrast the cell wall of Gram-positive and Gram-negative bacteria by building your very own bacterial 3D models on the hologram table. Enter the exploration pod to observe in an immersive animation how the four reagents of the Gram stain interact with structural components of the cell wall to color the bacteria. Perform the gram stain When the patient’s fluid sample arrives at the laboratory, equip yourself with protective gear to prepare a bacterial smear and heat fix it to a glass slide. You are now ready to perform the Gram stain in a safe virtual environment. Made a mistake? No worries, hit the big red button on the workbench to repeat the staining procedure until it becomes second nature. Interpret your findings using a microscope In the end, you will use a light microscope to interpret the results of your Gram stain. View the microscopic image on the computer screen, and apply immersion oil to increase magnification 1000x! Will you be able to identify the presence of any bacteria in the patient´s cerebrospinal fluid? Questions: 1. Purpose: Please describe in complete sentences and in your own words, the purpose of this experiment. The purpose of this lab experiment was to differentiate between the gram negative and positive bacteria , how to preform a gram test and learn the steps involved in 1

BIOS242, Week 3-OL Name:

doing this test as well as the differences between the cells of a gram negative and positive cell . 2. Complete the following table by predicting colors of bacteria with- and without cell wall as they are processed through the steps of Gram staining.

Steps of Gram Staining Crystal violet treatment Iodine Decolorization Safranin

Bacteria containing thick cell wall Purple Purple Purple Purple

Bacteria containing thin cell wall (LPS) Purple Purple Colorless Pink/Red

3. A fellow student showed you a gram-stained slide where cells containing thick cell walls were stained pink. What would you tell her about the staining procedure? Why?

I would inform the student that she most likely over-decolorized the slide. When too much decolorizing agent is used or it is left on for more than 15 seconds then all the bacterial cells will stain pink or red and appear as gram-negative. Since the thick walls is indicative of being gram-positive and should be stained purple. 4. A fellow student showed you a gram-stained slide where cells containing LPS were stained purple. What would you tell her about the staining procedure? Why?

I would tell the student that Lipopolysaccharide (LPS) is only found in gram-negative bacterial . These cells should be stained pink so if stained purple then it means that the slide was not colorized enough. This is because too little alcohol was added or when the decolorizing agent was not left on long enough. I could do over the procedure and show my classmate the correct way . 5. Reflection: Write 5 sentences on what you learned from this simulation. What did you like and what was something that you would prefer not be a part of this simulation?

From this stimulation I learned that gram bacteria appears purple and gram negative bacteria appears pink . In order to diagnose a patient with bacterial meningitis a CFS sample should be taken and sent to the lab . A gram stain will be preformed on this sample to determine whether or not the patient has this disease . Gram stains takes only a few minutes to preform

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BIOS242, Week 3-OL Name:

so it is a very efficient test . The use of positive and negative controls are used to ensure that the stain was preformed correctly . This is a way that one is able to ensure that they are preforming the test in the proper way . Visualizing the cells under a microscope and making note of the shape and color that was taught in the lecture then seeing how it looks made the concept much easier to understand . I liked that I was able to preform a virtual gram stain in the labster. It was something that I enjoyed especially when I messed up , it made me do it again until I was able to figure out what I did was wrong. The one thing I dislike is that the labster is such a slow and temperamental program that it often freezes and therefore ends up taking up a lot more time to get through the assignment . I also wish that I was able to preform this experiment in a real lab setting .

Grading Rubric: Activity Lab Report and Questions

All Lab Deliverables

Deliverable Complete lab report and answer questions 

Purpose (1 point)



Questions (9 points)

 Reflection (5 points) Complete ALL lab work and lab report

Points 15

15

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