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19.5: Post-lab Questions

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    1. Explain why gram + bacteria stain purple, what happens during the decolorization step, and why Gram-cells stain pink.
    2. What is the function of the Iodine step?
    3. Were you able to distinguish between G+ cells and G- cells? Give the gram reactions of E. coli and S. saprophyticus.
    4. Why is the acetone/alcohol step the most critical step in the process?
    5. If you observed bacteria from a single colony that were gram variable,
      1. What other characteristics could you use to help you identify the organism?
      2. How might the age of the culture affect the results?
    6. What would happen if you Gram stained E. coli, but forgot the decolorizing step?
    7. What would happen if you Gram stained S. saprophyticus and forgot the decolorizing step?
    8. Explain, in your own words and experience, whether or not your smear prep was done appropriately for this stain.

    Contributors and Attributions

    This page titled 19.5: Post-lab Questions is shared under a CC BY license and was authored, remixed, and/or curated by Kelly C. Burke.

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