Microorganisms are always around and ready to contaminate your carefully grown cultures. In this practical we will determine what common airborne contaminents look like.


  • 1 Peptone agar (PA) plate, favourable to bacteria
  • 1 Malt agar (MA) plate, favourable to yeast and fungi

In case you have no clue how to make Agar plates, please take a look at the Microbiology at Home manual of Dr. Simon Park. You will need a pressure cooker to sterilize the mediums.


  1. Find an interesting spot in the building.
  2. Remove the lid from the plates and leave the plates for 30 minutes.
  3. Collect the plates.
  4. Incubate at 30° C for 24h.
  5. Inspect your plates and look at them under the microscope.

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