OL_Gram_staining

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Chamberlain University College of Nursing *

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242

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Biology

Date

Dec 6, 2023

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docx

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Uploaded by CommodoreLyrebird3134

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 experiment is to determine the gram stain of the bacterial sample. It is used to determine the chemical makeup of the cell wall. The stain color will determine if it is positive or negative. It can also be used to determine the cells shape, size, and arrangement. 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. 1

BIOS242, Week 3-OL Name: Steps of Gram Staining Bacteria containing thick cell wall Bacteria containing thin cell wall (LPS) Crystal violet treatment Purple Purple Iodine Purple Purple Decolorization Purple No color Safranin Purple pink 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? A stained slide where cells containing thick cell walls where stained pink is a gram-positive bacterium. An error occurred during the procedure during one of the steps. For this slide, the Iodine step was skipped over. The crystal violet would initially bind equally. Thus, adding the Safranin stained the bacteria pink. 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? A gram-stained slide where cells containing LPS were stained purple because of an error that occurred. Gram- negative cells contain LPS that are found in the outer membrane of the bacteria. The step where alcohol is used to decolorize the sample was missed. Without this step, the crystal violet and iodine were not washed away. Thus, leaving a gram-negative bacterium to be stained purple. 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? In this lab simulation, I learned about the different components of both gram-positive and gram-negative and how they are both structurally different. I also learned why they stained the color the way they did based off their components like their peptidoglycan and thick cell wall. I also learned the steps of how-to gram stain a cell and how to do the procedure myself. I was even able to look into a microscope and tell the difference between the gram positive and negative along with their structure, size, and arrangement. I liked this simulation a lot because everything was informational, and it did not skip a step. I felt that it was made as real as possible it could be. 2

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