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Materials: • Cotton swabs • 2 Petri dishes • Permanent marker

Using a swab, take a sample from inside the nose of a classmate. Plate the sample in a Petri dish following the instruction in activity Nº2.

Do not forget to label the Petri dish! At the same time, use another swab to take a sample from inside the mouth (tongue or cheek) of another classmate and repeat the procedure.

Incubate the labeled plates in a warm place, with the agar facing upwards and with no direct light during 48 hours. Then, observe the microorganisms growing in each of the plates. Analyze the colonies comparing color, texture, form, etc. After two days, you can store the plates in a refrigerator (4 a 6ºC) for a couple of days.