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3.11: Determination of Bacterial Numbers

  • Page ID
    90988
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    Plate Counts

    Preparation

    • sterile TSB in test tubes on hand for E. coli cultures (1 per group)
    • TSA plates (4 per group)
    • Sterilize:
      • microcentrifuge tubes (7 per group)
      • tips for pipettes (for pipettes that can dispense 990 μL and 100 μL)
    • inoculate sterile TSB in test tubes with E. coli 8-16 hours before lab and incubate at 37 °C (1 per group)

    Materials

    • sterile microcentrifuge tubes (7 per group)
    • sterile tips for pipettes (for pipettes that can dispense 990 μL and 100 μL)
    • pipettes for dispensing 990 μL and 100 μL (enough for each group or for two groups to share)
    • containers for used pipette tips
    • 8-16 hour E. coli cultures in TSB (1 per group)
    • TSA plates (4 per group)
    • vortex (enough of them for groups to share)
    • labeling marker (1 per group)
    • spreader tools (1 per group)
    • ethanol in squirt bottles
    • empty petri plates (1/2 per group)
    • Bunsen burners (1 per group)
    • strikers (1 per group)

    Absorbance Measurements

    Preparation

    • test tubes with 5 mL sterile TSB (4 per group)
    • inoculate sterile TSB in test tubes with E. coli 8-16 hours before lab and incubate at 37 °C (1 per group) - if the plate counts are being done with the absorbance measurements, these are the same cultures used for the plate counts

    Materials

    • test tubes with 5 mL sterile TSB (4 per group)
    • 8-16 hour E. coli cultures in TSB (1 per group)
    • pipettes for transferring 5 mL (enough for each group to complete four transfers
    • transfer pipettes (5 per group)
    • cuvettes
    • waste container for E. coli samples emptied from cuvettes
    • spectrophotometer set to 600 nm (enough for two groups to share)
    • labeling tape (1 per group)
    • labeling marker (1 per group)

    Creating a Standard Line between Plate Counts and Absorbance

    Materials

    • graph paper or computers with graphing software (1 per student)
    • rulers (1 per student if using graph paper)

    This page titled 3.11: Determination of Bacterial Numbers 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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