Page:Bacteria, why do they make me sick?.pdf/52



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

Grab a cotton swab and swipe it over the surface of any object around you, such as a table, chair, toilet, cell phone, etc. This process is called sample collection or sampling.

Then, apply the sample to a petri dish from activity Nº1, rubbing the swab in a zigzag pattern. This process is called inoculate or plate.

Then, place the lid on the Petri dish and label it over the external side of the dish, writing down the place where the sample was collected, the name of the person collecting the sample and date. Do not label the lid. This process is called labeling. Repeat the steps of sampling, plate, and label for each place you want to analyze.

The incubation process consists in placing the inoculated plates in a place where bacteria can grow. Leave the plates upside down at room temperature for 48 hours and in a place with no direct light. Then, analyze the colonies present in the agar and compare color, texture, form, etc.

After two days, you can store the plates in a refrigerator (4 a 6ºC) for a couple of days.