9 GRAM STAIN AND MICROSCOPE SKILLS ASSESSMENT
ASSESSMENT CRITERIA
Aseptically transfer bacteria to liquid and solid media
Perform streak plate technique resulting in isolated colonies
Describe bacterial colony morphology
Properly make a bacterial smear for staining
MATERIALS
Unknown slant culture of one organism:
Staphylococcus epidermidis
Escherichia coli
Lactobacillus fermentans
Neisseria sicca
Equipment:
Glass microscope slides
Water dropper bottle
Inoculating loop
Bibulous paper
Cotton swabs
Microscope
Immersion oil
Stains:
Crystal Violet
Gram’s Iodine
Acetone-alcohol
Safranin
Properly using a microscope, correctly performing the Gram stain procedure, and evaluating the Gram stain results are basic skills necessary for all microbiology students. These skills will be utilized throughout the semester, including the end of the semester to identify your Mixed Unknowns.
PROCEDURE
1. You will be given an unknown bacterium on a TSA slant.
2. You may use the Lab Manual.
3. DO NOT HELP EACH OTHER. This is an individual skills assessment.
4. Make a few bacterial smears with your unknown.
5. Gram stain the slide, focus the specimen on oil immersion and observe the known bacteria on each end of the slide. Evaluate how well you decolorized the smear.
6. If your decolorization was successful, then observe the unknown bacteria and determine the cellular morphology and Gram stain reaction.
7. Keep the specimen focused on the microscope. Record your results on the worksheet, then ask the instructor to check your results.
8. After cleaning your microscope and properly preparing it for storage, ask your instructor to check your microscope for correct microscope cleanup.
