Lesson 5: Microbes All Around Us

Youth sample microbes from high touch surfaces such as cell phones, doorknobs, and computer keyboards.

Key Teaching Points

  1. Microbes can be found in many places: on our hands, inside our bodies, and on objects that we use every day.
  2. Colonies of bacteria can grow large enough to see without the use of a microscope.
  3. Bacteria or fungi can cause various illnesses.

Learner Outcomes

  • Compare and contrast microbes as they grow in a nutrient solution.
  • Examine various surfaces and graph the bacteria present.
  • Create a cartoon/poster showcasing what has been learned from the lesson.

Skill Level: 6-8th grade

Success Indicators

  • Participants will create and present a product/deliverable explaining microbial growth.
  • Participants will complete a plating activity and graph.

Life Skills

Critical Thinking, Communication, Problem Solving, Teamwork, Presenting

Time Needed

1-5 days

Space

  • A clear area on table or countertop that has been cleaned thoroughly with a disinfectant

Suggested Group Size

No more than four participants per group

 

Acknowledgments

Ron Dunn Lab  – Belly Button Biodiversity

Materials

Materials List

Each individual participant should have:

  • science notebook/journal
  • Pen/pencil
  • Youth handouts 

The items listed below should be made available per group of four:

  • One petri dish with agar solution (4-inch size) per participant
  • Cotton swab
  • Tape
  • Disinfectant
  • Permanent Marker 
  • Safety gloves
  • Hand lenses
  • Alcohol swabs 
  • Posterboard
  • Plastic pipette 
  • Bleach solution
Directions for the disposal of petri dishes

Once all bacterial growth has been documented on the last day of the experiment, safely destroy the colonies grown. Untape the lid of the plate and then slowly lift the plate at an angle and pipette in about 20-30 mL of a bleach solution. Close and retape the plate. Let the plates stand for at least an hour undisturbed. The plates can then be safely thrown into the trash.

NOTE: This step MUST be completed with gloves ON.

Introduction

Introduction

Microbes can be found in many places: on our hands, inside our bodies, and on objects that we use every day. Likewise, they may also be found in the air, water, and soil. Bacteria are the most common living microbes. They are extremely small cells that must be magnified many times to be visible. A microscope is used to view individual bacterial cells. However, colonies of bacteria can grow large enough to be seen without the use of a microscope.

Microbes called fungi are valued for their ability to obtain energy from food sources through a process known as fermentation. This process is vital in the production of alcoholic beverages, bread, and other baked goods because it produces alcohol and carbon dioxide gas.

In some instances, bacteria and fungi can cause various illnesses. If fruits, vegetables, or meats become contaminated by these organisms, they are then unsafe to eat.

Before the Activity
  • Ensure that you have secured all the necessary materials.
  • Prepare technology to show the presentation to the class.
  • Prepare copies of the Microbial Math worksheet (one per participant).
  • Prepare copies of the Microbes All Around Us Participant Data Sheets A, A-1, and A-2 (one per participant).
  • Prepare copies of the Microbes All Around Us Lab Reflection (one per participant).
Note about participant research

Beginning on Day 2, participants will start a research component for this lesson. Groups will present their research posters on the final day of observation of the Petri dishes. Decide ahead of time if the research will be self-directed or if specific areas of research will be assigned to each group.

Areas of focus can include:

  • microbial growth
  • personal hygiene
  • food safety practices
  • types of pathogenic microbes
  • specific types of illness caused by microbes
  • any other topic you feel would be informative for the class as a whole

Participants should link the microbe growth on their Petri dishes into the research in some way. This may look different for each group, depending on the topic and what the group has cultured on their Petri dishes.

Lesson

Opening Questions
  • Has anyone you know ever had pink eye? Pneumonia? Food poisoning?
  • How did they feel when they were infected?
  • How did you think they got this disease?
  • How did you feel or act around these people when they were infected?

Follow-up questions:

  • Does anyone think there are any microbes in this room?
  • Where might they be?
Let’s Do It!
  1. Show the presentation to the class.
  2. Ask participants if they know why we cook food or keep it in a refrigerator. Explain that putting food in the refrigerator only slows or stops microbial growth; it doesn’t kill the microbes. The microbes will grow again when they come out of the refrigerator. The only way to kill microbes is to cook food until it is really hot and cooked all the way through. This is because very warm temperatures kill many harmful microbes.
  3. Ask participants about safe handling procedures for food. How should food be handled to maintain safety? Have participants list some safe and unsafe procedures for handling food that is ready to be eaten.
  4. Ask the Opening Questions.
    • Has anyone you know ever had pink eye? Pneumonia? Food poisoning?
    • How did they feel when they were infected?
    • How did you think they got this disease?
    • How did you feel or act around these people when they were infected?
  5. Facilitate discussion among the participants. Ask participants if they believe the “five-second rule” to be truth or fiction. Allow participants to defend their position.
  6. Introduce the Microbial Math worksheet. Follow the scenario on the worksheet to help participants understand the connection between bacterial contamination and growth.
  7. Explain that in this lesson, participants will swab various locations that are encountered on a daily basis to investigate whether or not diverse microbes are truly present. If present, different types of microbes will be collected from the swabbed samples and transferred to a pre-prepared petri dish. Colonies should be observed growing on the agar over a period of 3-7 days.
  8. Ask participants the Follow-up questions.
    • Does anyone think there are any microbes in this room?
    • Where might they be?
  9. List their ideas on the whiteboard or chalkboard.
  10. Share that the class is going to find out if any microbes are present in the room or even on some of the items that the participants use every day.
  11. Divide the participants into four groups of no more than five participants per group. Assign participants in each group one of the following items to swab. Each member of each group will swab and culture a petri dish of their own.
    1. Cell Phone or another personal electronic device
    2. Belly Button
    3. Door Handle
    4. Pen, Pencil, or Book
    5. Computer Keyboard
Review of safety guidelines with ALL participants
  1. All materials (book bags, clothing) other than laboratory materials should be off of the work area. NO EATING!
  2. Wear the safety gloves provided.
  3. Long hair must be tied back.
  4. Clean off the workstation with the disinfectant solution (commercial product or 10% bleach solution) BEFORE and AFTER lab activities.
  5. Wash hands BEFORE and AFTER lab activities with hand soap.
  6. Avoid placing any lab materials in your mouth.

**CAUTION: After the completion of the activity, make sure all participants follow proper lab cleaning protocol. Do not allow bleach to touch skin, eyes, or clothes. It may burn!

Day One
  1. Select one unused petri dish.
  2. Label the bottom of the petri dish with the assigned sample being tested and your name.
  3. Use a permanent marker to draw an X on the top of the petri dish.  This will divide your petri dish into quadrants and make it easier to count any colonies that grow.
  4. You will now collect some microbes on the end of a cotton swab.
  5. Roll the swab across your designated item or area and then lightly draw a wavy line with it on the gelled agar.
  6. Place the top on the petri dish. For your protection, tape the petri dish closed. For safety reasons, DO NOT re-open the petri dish; you could be culturing a pathogen. You can view the growing microbes through the clear dish.
  7. Turn the plate upside down and then place the plate in a warm, dark place to grow for three days. You can look forward to seeing a variety of microbes growing in a few days. As time increases, more colonies will grow and increase in size.

NOTE: Any temperature up to about 98° degrees F (37° degrees C) should be fine. Examples of warm places include, but are not limited to: the top of a refrigeration unit, a sunny window, or the inside of a drawer. If this activity is being conducted during the winter months, consider setting up an incubation area with a grow lamp or another warming device that can be monitored for safety while you are present. Warming devices may be turned off when unattended.

Day two through day four
  1. Begin the research portion of this lesson. In their small groups, participants will conduct research as assigned. Suggestions for participant research are listed in the Before the Activity section above.
  2. Explain to participants they are to display the results of their research as a group. Each display should include at least a one page summary of the group’s findings. Encourage participants to organize their displays as creatively as possible. They can include comic strips, infograms, diagrams, charts, graphs, or any other method that conveys the information in an interesting and informative way. Alternatively, participants may create an electronic presentation as technology is available.
  3. Examine the Petri dishes each day at the same time WITHOUT opening them.
  4. Record all data on Participant Data Sheet A each day.
  5. Compare and discuss the growth results with two other participants each day. Document their results on Participant Data Sheets A-1 and A-2.
  6. Compare your results to the findings at:  Rob Dunn Lab
Day Five (or end of observations): Present and Network Like A Scientist
  1. Ask the Share questions.
    • What has changed inside the petri dishes?
    • Were you surprised about the microbes that grew in the area your group tested? Why or why not?
    • Why do you think your area had a significant growth of microbes?
    • Comparing your data to the other groups, which area tested seemed to have the most microbial growth? Why do you think this occurred?
    • Which area had the least microbial growth? Why do you think this occurred?
  2. Ask the Generalize questions.
    • Do your results prove or disprove that there are microbes everywhere?
    • With all these bacteria growing, why do you think people aren’t more sick or sick more often?
    • What does the information gained from this experiment tell you about human hygiene?
    • What new questions did your results bring up?
  3. Give each group a few minutes to present their posters as well as to observe those of their peers.
  4. Discuss and document the similarities and differences among their findings.
  5. Ask the Apply questions.
    • What are some measures people could take to prevent the spread and growth of microbes?
    • From this activity and your research, will you change any of your hygiene practices? If so, which one(s) and why? Explain your answers.
    • Have you noticed signs in almost all public restrooms stating that all employees must wash their hands before returning to work? Why is this important and how is it relevant to what you have learned in this lesson?
  6. Participants will complete the Lab Reflection.
Assets
Comic Page
Microbes All Around Us Presentation
Microbial Math
Data Sheet A
Data Sheet A-1
Data Sheet A-2
Lab Reflection
Vocabulary Flashcards – Quizlet

Dig Deeper

Have your students complete this writing prompt
  • You have been tasked with promoting the growth of a bacteria known to heal cancer when consumed. How does this bacteria grow? How are you making sure this bacteria thrives? Use what you already know about bacteria growth to tie this in.

This work was supported by a USDA-NIFA grant #2012-68003-18621

USDA

Partnered with:

NC State University
4-H Clover
Kenan Fellows Program