Handwashing: Microbes Around Us

  • Introduction
  • Video & Results
  • Materials
  • Procedure
  • Preparation & Notes
  • Download Files


The term "microbe" is short for microorganism, which by definition is a living thing that is too small to see without magnification. Microbes can be bacteria, tiny plants, fungi and other living things. Although microbes can't be seen without microscpes, when deposited onto a nutrient rich medium, many will reproduce and form colonies. In this excercise, students get a chance to transfer microbial life from their finger to a plate before and after washing hands. If the plates are kept at room temperature for 2-3 days (Day 1 Friday/Day 2 Monday), colonies will appear for the second meeting for the experiment. Students also choose locations in their environment that they expect to find microbes. This activity is often timed with the beginning of flu season to illustrate the importance of handwashing and what kind of organisms are in their environment.

During this excercise students are also reminded that microbes have essential roles in daily life, including in yogurt production, yeast fermentation processes and nitrogen fixation.

Handwashing plate

Classroom Swabs



  • 1 soy agar plate /student plus extras for room swabs (Teknova TO144 20 plates/$20)
  • sterile swabs
  • sharpie pens
  • tape

Activity 1 : How clean are your hands?

  1. DO NOT OPEN THE PLATE.  On the plastic bottom, write your name and draw a line down the center of an agar plate.
  2. Write “D” (dirty) one one side and “C” (clean) on the other.
  3. Taking the lid off the plate for a short period of time  gently run a finger on the agar of the “Dirty” side of the plate.
  4. Now wash your hands with soap and water for 30 seconds.  Carefully dry your hands with a clean paper towel.
  5. Gently rub your clean fingers on the other half of the plate.
  6. Allow your plate to incubate with agar side on top for 2-3 days.
  7. After incubation, DRAW what you see on your plate.

Activity 2 : Swabbing your environment

  1. Discuss with your group a place to test for microbes.
  2. Gently swab the location with a sterile Qtip.
  3. Gently run the Qtip on a new agar plate.
  4. Allow your plate to incubate agar side up for 2-3 days at room temperature.
  5. After several days, DRAW what you see on your plate.



  • We have used hand sanitizer, which is preferred by some hospitals for soap washing. It is important to make sure that hands are dry before rubbing the clean side.
  • Interesting swabs: floors, shoes, yogurt, mouths, computer keyboards
  • It's useful to have students rank the amount of growth they see in each area, one plate at time to foster discussion
  • Tape the plates closed after swabbing so that students don't open them
  • If enough growth occurs before you can meet with students, put plates in a refrigerated area to arrest microbial growth. Otherwise the plates get overgrown and difficult to describe.

Booklets printing:

  • 1st Grade level (powerpoint) (pdf) This booklet is appropriate for 1st grade. The paper should be printed on both sides. The powerpoint layout should be selected to have 2 pages per sheet. The pdf has the layout already integrated into the pagination for printing landscape.
  • 3rd Grade level (powerpoint) (pdf) This booklet has a bit more detail and reading material for students and also talks about gram staining. These are printable files that are designed to be folded (& shuffled) into a booklet if printed on 2 sides. Print landscape with binding on short edge.