Microbiolgy

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Microbiology 197
Prepared Bacteria Gram Stains (F12)

Materials required:
* Microscope; clean and properly set up
* Immersion oil
* Lens paper
* Lens cleaning fluid
* Microscope drawing forms
* Specimens: 1. Bacillus subtilis
2. Staphylococcus aureus. 3. Escherichia coli

Procedure:
1. Observe each of slides listed in “Specimens” above.
2. Make your observations using oil immersion (1000X).
3. Using a drawing form draw the organisms you see using proper scale and proportion. 4. Provide the following “Observations” in the space to the right of the drawing circle: a. Gram reaction (color and interpretation)

b. Morphology (shape)
c. Arrangement (how did the bacterial cells appear in relationship to each other) 5. Remember, all data lines must be filled in. This will include your name, laboratory title, date, subject, magnification, and observations.

** Record what you see, not what you think you should see.

Answer the following questions: (Use your notes, text and or laboratory manual) 1. How will a microbiologist use this staining method to begin the identification of bacteria? Microbiologists use this staining method to begin the identification of bacteria because it will allow them to tell the four different categories based upon color reaction and shape. It is the first step that will help in identifying bacteria. The structural variations found in the cell walls of bacteria will determine the color of the stain; blue (positive) or red (negative).

2. Give one specific clinical reason for gram staining a patient's sputum specimen. One specific clinical reason for gram staining a patient’s sputum specimen would be to isolate and identify microorganisms causing an infection of the lower respiratory tract. Examples would be tuberculosis or bacterial pneumonia. A gram stain is always performed when sputum is submitted for culture and used to determine the...
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