Lesson Plans Grades 4 to 8
:: Lesson Plan #19: Growing Micro-organisms
Learning Objectives
- Students will grow micro-organisms by making cultures on agar plates.
- Students will recall that hand cleaning reduces the number of bacteria on hands.
Materials
- Petri dishes, nutrient agar (get these from a science teacher, university, or hospital).
- Masking Tape and Scotch Tape
- A marker
- Cotton swabs
- Handwashing facilities
- Liquid soap
- Toothpicks
Key Messages
- Micro-organisms can be everywhere.
- Hand cleaning reduces the number of bacteria on hands.
Method
Students will
- Inoculate petri dishes with a different bacterial source for each plate.
Suggestions are:
- Hair – place a human hair into the dish.
- Cough – hold a petri dish about 6 cm away from the mouth of a student and have him/her cough onto the plate.
- Saliva – place a clean cotton swab into a mouth and moisten it with saliva; rub the swab over the agar.
- Nose – place a clean cotton swab into a nose and gently move it around, rub the swab over the agar.
- Counter – have a student drag his/her fingers on a counter top then trace an “S’ on the agar.
- Fingernail – scrape underneath with a toothpick and place contents into the dish.
- Place the imprint of a washed fingertip in the agar in a petri dish.
- Place the imprint of an unwashed fingertip in the agar in a different petri dish.
- Tape each dish closed by running scotch tape around the edge.
- Place the dishes in a warm dark place for three to five days.
- Check the dishes daily for growth; when the desired amount of bacteria growth is seen, refrigerate.
- When bacterial growth can be seen, examine dishes and discuss how the bacteria became present.
- Recall the different routes of transmission that occurred when inoculating the petri dishes.
- Examine and compare all the cultures in the dishes. Explain how hand cleaning reduces the amount of bacteria on hands.
Activity
- What are the implications of this experiment for classroom hygiene and hand hygiene?
- What would you do differently regarding hand hygiene at school and at home?
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Adapted with permission from Wellington-Dufferin-Guelph Health Unit.
