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Microbiology

Aseptic technique, growth media and inoculation

  • 3 things to know
  • A2 6

Overview

Aseptic technique and flaming loops, disinfection and sterilisation, preparing media and filter sterilisation, streak, pour and lawn plates, mycelial discs, plaque assays and safe incubation.

What you need to know

Answer each one before you reveal it.

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Key term

What is aseptic technique?

Key term

How is an inoculating loop sterilised?

Key term

Why is work carried out close to a Bunsen burner flame?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is aseptic technique?

    Model answer

    Aseptic technique is the set of practices that prevent unwanted microorganisms contaminating a culture. The same practices also stop the culture escaping into the environment.

  2. 2

    How is an inoculating loop sterilised?

    Model answer

    The loop is heated in a Bunsen flame until it glows red hot. The loop is cooled for a few seconds before it touches the culture, so the microorganisms are not killed.

  3. 3

    Why is work carried out close to a Bunsen burner flame?

    Model answer

    The flame creates an updraught of hot air. Airborne microorganisms are carried away from the open culture.

  4. 4

    What is the difference between disinfection and sterilisation?

    Model answer

    Disinfection reduces the number of microorganisms on a surface to a safe level. Sterilisation kills or removes all microorganisms, including spores.

  5. 5

    How is a growth medium prepared and sterilised?

    Model answer

    Nutrient powder and agar are dissolved in water and heated. The medium is then autoclaved before being poured into sterile Petri dishes.

  6. 6

    How is a heat-sensitive solution, such as an antibiotic, sterilised?

    Model answer

    The solution is passed through a membrane filter with pores about 0.2 µm across. Bacteria are trapped, and the filtered solution is sterile.

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