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The Human Microbiome

The Human Microbiome offers an opportunity to learn about microbiology and ecology. Here is a collection of companion activities to help explore the subject further.

Human Microbiome Assessment Items (pretest): PDF or Word

Human Microbiome Assessment Items (posttest): PDF or Word

Your Microbial Friends Worksheets

These templates are designed to help students organize and take notes on the beneficial microbes covered in the Your Microbial Friends activity on Learn.Genetics. Both worksheets focus on the important concept that microbes perform beneficial functions all over the body.

Sample Post-Activity Discussion Questions

  1. Which area of the body seems to have the highest concentration of beneficial microbes? (In the gut)
  2. What is the role of microbial genes? (They code for the proteins that do the work)
  3. Do you suppose the beneficial functions of microbes are affected by antibiotics?

Each PDF contains copy masters and an answer guide.

Symbiotic Microbes

Contextual clues help students match commensal or mutualistic microbes to the area of the human body where they thrive. Includes easy-cut cards featuring eight example microbes and an outline of the human body with space to record answers. Have students work individually or in groups.

Adaptations/Extensions

Continue the connection to themes in ecology by having students brainstorm which abiotic factors each example microbe faces.

Symbiotic Microbes PDF

Symbiosis Scramble

Make enough copies to give each student two cards: one of each color. Keep the cards grouped by color and shuffled.

Students role-play gut-dwelling bacteria with different properties (determined by cards they pick) and try to form different symbiotic relationships. This activity demonstrates the difference between Mutualism, Parasitism, Commensalism, and Competition.

Symbiosis Scramble PDF

Culturing Microbes

Have students culture swabs from their skin to "prove" to them that there is indeed an ecosystem of microbes living there! A few simple steps can lead to an engaging exploration of the following concepts:

  • Microbial ecosystems exist on the skin, even though we can't see them.
  • Microbial ecosystems differ from person to person.
  • Microbial ecosystems differ among locations on the body.

You may have all students swab the same area of skin to comapare differences among individuals.

You may have students swab multiple areas of their skin to compare the microbial communities found there. Swabs from each area of skin can be cultured in separate agar plates, or in separate areas of the same plate ("divide" the plate into different areas by drawing lines on the outside of the agar-containing side of the plate).

Distribute To Students:

Pre-poured agar plates (For tips on making your own inexpensive plates, see Making Agar Plates.) Instruct students to keep their plate lids closed to avoid contamination.

Sterile swabs or store-bought cotton swabs. Instruct students to handle only the stick part of their swab to avoid contamination.

For a primer on sterlie technique, see Sterile Technique.

Give students the instructions below.

Student Instructions

  1. Choose an area of the skin to swab. Ideas include the crook of the elbow (Antecubital fossa), the crease on the side of the nose (Alar crease), between the toes, or inside forearm (Volar forearm).
    Hint: Encourage students to choose a less obvious source of microbes than the hands.
  2. Label the outside of your pre-prepared agar plate(s) with your name or other identifier and the location on the skin you will swab.
  3. Handling only the stick part of the swab to avoid contamination, gently rub the swab over the area of skin you've chosen.
  4. Lift the lid of your agar plate and gently rub the swab in a zig-zag motion across the agar. The swab should lightly abrade the surface of the agar, but not dig in to it.
  5. Close the lid of the agar plate, and seal the edges with parafilm or tape.
  6. Incubate and compare. Incubate the plates upside down at about 37°C in the dark for 24 hours. (A warm dark space in the room such as a closet or box would work too—it will just take longer for growth to appear, around 2-4 days). Keep the plates sealed.
  7. Keeping the plates sealed, observe and compare microbial growth on the plates.

    Hint: If condensation on the plate lid is making it hard to see, gently flick the lid with your finger.

    Note: The microbiomes of some students may flourish more than others due to personal microbial ecology or lab technique.
  8. Dispose of the sealed plates properly.

Notes:

The plates of cultured skin swabs could possibly contain species of Staphylococcus bacteria and other potentially pathogenic microbes in amplified amounts. Once the plates are swabbed, it is very important to keep them sealed to prevent exposure to these microbes.

The microbes that grow on the agar plate represent just a fraction of those found on the skin. Most microbes that live on the human body are adapted to live in a specific ecosystem and cannot be cultured.