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  Lesson 1B Laboratory
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High School Food Safety Lessons

Lesson 1B Bacteria Everywhere
Laboratory Lesson

National Health Education Standards
(grades 9-11) 1:1, 1:5
introduction
  1. Emphasize with students that bacteria are everywhere and can spread from surface to surface, person to person, food to food, and person to food. Explain to students that harmful bacteria can be controlled by practicing what is called the 4Cs of Food Safety—Clean, Cook, Chill, and Combat Cross-Contamination.
  2. Reinforce with students that not all bacteria are harmful; most bacteria are beneficial—and give some examples (see page 6 of Food Safety A to Z Reference Guide).
activity 1
  1. State:
    “Today you are going to look at how the bacteria have grown in your Petri dishes and record the results. You can turn over your Data Table Sheet and illustrate the organisms that are growing.”
  2. Help students to analyze the results of their experiments.
  • Use a scale of 0-5 to enumerate the number of colonies you see.
  • State the size, shape, and colors of the organisms and record on the Data Table Sheet.
  1. Discuss:
  • Why do the microorganisms look different?
  • How can the different strains of bacteria be identified (by colony morphology)?
  1. Discuss:
    Place one of the Petri dishes on an overhead projector and discuss the characteristics.
activity 2
  1. Question:
    “How do you know the agar and swabs used to collect samples were free from micro-organisms?” (Make a control plate.) If agar and swabs were contaminated, discuss how this would affect the results.
  2. Questions:
  • “What do the data you have collected have to do with food you eat?” (Bacteria can be transferred from surface to food and from hands to food.)
  • “Why do certain surfaces produce more bacterial growth than others?” (It depends on moisture, temperature, pH.)
  1. Discuss:
    All bacteria are not bad; in fact, most are beneficial (again, give examples).
activity 3
  1. Ask the students:
    “How can bacteria be transferred from objects to foods, from people to foods, and from food to food?” (Contact with contaminated objects, hands, other foods)
  2. Discuss:
  • Why is it important to more thoroughly clean some surfaces than others? (Bacteria thrive in some areas more than others.)
  • How should surfaces be cleaned?
  • What advice do you have for restaurant workers and fast-food employees?
Closure
Share with the students:
“This laboratory lesson continues to reinforce understanding of different strains of bacteria and how these strains can be identified through colony morphology. It also reinforces our knowledge about how bacteria can be spread from surface to surface, from person to person, and from food to food. The simple rules that we can all remember is: Clean, Cook, Chill, and Combat Cross-Contamination. In our next lesson we will discover the 12 most unwanted bacteria—or pathogens (a pathogen is any micro-organism that is infectious and causes disease).”
Integration ideas
Seek school personnel cooperation by:
  • Asking the librarian to place Dr. X and the Quest for Food Safety video on reserve so that students can review Module 1, Understanding Bacteria.
  • Asking the English department to encourage students from this class to prepare a report discussing the effects the 4Cs have on bacteria. Explain that students should cover Cleaning (removes bacteria from hands and surfaces, Cooking (heat kills bacteria by breaking down their cell walls), Chilling (slows down the bacteria's metabolism thus slowing growth), and Combatting Cross-Contamination (prevents the spread of bacteria from one object to another).
  • Ask a microbiologist, surgeon, hospital dietician, school cafeteria director, emergency room physician, meat-packing employee, or milk processing plant employee to discuss their work with your class as a reinforcement of the concepts learned. Be certain to inform the speaker about the level of student insights gained from the two laboratory lessons, and the relationships drawn to food safety, so the speaker can explain how he/she controls the spread of harmful bacteria.
  • Provide classroom or school library with a copy of Food Service Education: Community Service Learning Curriculum. A Program Using the Community Service Learning Model to Teach Youth Food Safety, Volumes I and II (Project Team: Lori Pivarnik, Ph.D., Co-Principle Investigator, and Martha Smith-Patnoad, Co-Principle Investigator) University of Rhode Island, Department of Food Science and Nutrition Cooperative Extension. This program was designed for Extension educators and their collaborators to provide training and support for FCS teachers who want to integrate food safety based community service learning into existing programming. The Extension educator provides 6-8 hours of training for the teachers with an emphasis on food safety principles and on the community service learning model.

    Please refer especially to Teacher Information sheets 1-9, Teacher Fact Sheets pages 52-78, and Student Activity #1, #2, and #3 (page 79-91), which are especially related to these lessons.

Provide students with the following resources and websites:

  • The Microbe Zoo: Digital Learning Center for Microbial Ecology at Michigan State University/Comm Tech Lab www.comtechlab.msu.edu/sites/dlc-me/zoo/
  • What are Germs? Kids Health www.kidshealth.org/kid/talk/qa/germs_prt.htm
  • Why Do I Need to Wash My Hands? Kids Health www.kidshealth.org/kid/talk/qa/wash_hands_prt.htm
  • It's a SNAP. Centers for Disease Control and Soap and Detergent Association
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Rhode Island Department of Education

Rhode Island Department of Health

University of Rhode Island

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