2. Explain the differences between smears from liquid and solid cultures. 3. Explain the need of smear to be air-dried. Air-drying adheres the bacteria to the slide. It also ensures that the smear is thin enough to stain 4. If you are given to make bacterial smear from liquid or solid media, with which one you are comfortable and why?
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Differences between smears from liquid and solid cultures: - Preparation: For a liquid culture, a loopful of the culture is directly spread on the slide. For a solid culture, a loopful of water is first placed on the slide, and then a small amount of the colony Show more…
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heat fixation "glues" the bacteria onto the slide. Too much heat can damage cell walls and distort the shape of the organisms. 4. With the clothespin still attached, place the slide onto a rack of a staining tray (specimen side up), allow to cool to room temperature. 5. Add a few drops of crystal violet to the specimen. Let sit for 1 minute, you may want to wear gloves while handling the stain. 6. After 1 minute, gently rinse the slide with water from the squeeze bottle on your bench to remove any excess stain. Allow the water to run down the slide held at an angle, do not pour water directly onto the smear. Gently shake off the water and allow the slide to air dry or blot dry with bibulous paper before examining your smear under the microscope. 7. Begin with a low power objective moving up to 100X. For the 100X (oil immersion) lens, you will need to place a drop of immersion oil on your specimen before examining it. Make sure that you thoroughly clean the lens with lens paper after use. Dispose the used slides in the red sharps container on your bench. Results: What is the morphology of the bacteria under the microscope? What color do the cells appear under the microscope? What color would you expect the cells to be if you used another basic stain- safranin that stains cells pink?
Keemin L.
1. Gram staining is a technique used to distinguish Gram positive microbes from Gram negative ones. In your own words, explain how the difference in cellular structure between these two types of cells allows them to be differentially stained. 2. What reagent behaves as a mordant? What would you expect to see in your stained samples if a mordant was NOT used? 3. Ibrahim was performing a Gram staining of a Staphylococcus aureus culture. When he looked under the microscope, he saw pinkish-red cocci cells. Did Ibrahim’s staining work properly? If not, what might he have done to get the results he saw? 4. Evelyn was performing a Gram staining of a Pseudomonas aeruginosa culture. When she looked under the microscope, she saw colorless bacillus cells. Did Evelyn’s staining work properly? If not, what might she have done to get the results she saw? 5. Rae was performing a Gram staining of an Escherichia coli culture. When they looked under the microscope, they saw pinkish-red bacillus cells. Did Rae’s staining work properly? If not, what might they have done to get the results they saw? 6. Ahna was performing a Gram staining of a Moraxella catarrhalis culture. When she looked under the microscope, she saw a mix of pinkish-red and purple cocci cells. Did Ahna’s staining work properly? If not, what might she have done to get the results she saw? 7. Travis was performing a Gram staining of a Bacillus subtilis culture. When he looked under the microscope, he saw a mix of purple bacillus cells and pinkish-red cocci cells. Did Travis’s staining work properly? If not, what might he have done to get the results he saw? 8. Connie was performing a Gram staining of a mixed, unknown culture. Just as she was about to put her slide under the microscope, her classmate pointed out that she had switched the crystal violet and the safranin in her protocol. Assuming Connie has both Gram positive and Gram negative cells in her culture, what would you expect her stained cells to look like under the microscope?
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How does the smear preparation technique from a broth culture differ from that of an agar culture? 2. Describe the steps taken to go from viewing the specimen at high power to viewing it under oil.
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