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3.5: Plating on Petri Plates for Isolation

  • Page ID
    90982
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    Preparation

    • sterile TSB test tubes (2 to grow cultures and another 3, 6, 9, or 12 [depending on how many cultures you want groups to share])
    • 3 TSA Petri plates per group
    • Inoculate TSB test tube with Escherichia coli and incubate at 37°C 24 hours before lab class
    • Inoculate TSB test tube with pigmented strain of Serratia marcescens and incubate at 30°C 24 hours before lab class
    • Just before lab class, aseptically transfer 200 μm of Escherichia coli culture to sterile TSB test tube(s) - add to 1-4 sterile TSB test tubes (E. coli cultures for students to use)
    • Just before lab class, aseptically transfer 200 μm of Serratia marcescens culture to sterile TSB test tube(s) - add to 1-4 sterile TSB test tubes (S. marcescens cultures for students to use)
    • Just before lab class, aseptically transfer 100-200 μm of Escherichia coli culture to sterile TSB test tube(s) and 100-200 μm of Serratia marcescens culture to the same test tube(s) - add to 1-4 sterile TSB test tubes (E. coli + S. marcescens cultures for students to use)

    Materials

    • 3 TSA plates per group
    • test tube racks (1 per group)
    • Bunsen burner (1 per group)
    • inoculating loop (1 per group)
    • markers
    • culture of E. coli
    • culture of S. marcescens (pigmented strain)
    • culture of E. coli + S. marcescens (pigmented strain)

    After Lab Class

    1. Incubate quadrant streak plates at 30°C for 24-48 hours.
    2. Refrigerate streak plates to prevent overgrowth if the next lab class occurs after 24-48 hours.
    3. Have students examine streak plates and characterize colonies next lab class.

    This page titled 3.5: Plating on Petri Plates for Isolation is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

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