To build on existing knowledge of microbes, focusing on the relationship between microorganisms and foodborne illness, as well as the implications that foodborne illness has on human health.
This lesson is the first in a two-part series on microbes. In earlier grades, students explored the health of the human body. They learned about deterrents to good health, such as tobacco, alcohol, and drugs. Research suggests that students of all ages may believe that factors important to health are beyond personal control. In addition, students in upper elementary school may think that all illnesses are caused by germs and are contagious. (Benchmarks for Science Literacy, p. 346.)
Microbes 1: What's Bugging Your? demonstrates that some "bad" microorganisms can get into the body through food ingestion. It explores environments that are supportive of food pathogens, as well as how humans can avoid contamination. This lesson is intended to build on a basic understanding of microbes. For example, students should already understand that not all microorganisms are "bad" and not all get into our body through food.
Microbes 2: Louis Pasteur–a Microbe Discoverer focuses on Pasteur and his discovery of microorganisms.
For a brief overview of microbes, read Meet the Microbes on the Microbe World website.
Students should already have had a basic introduction to microorganisms. Take this opportunity to find out what students already know.
Write the word "microorganisms" on the board. Draw a line between the two "o’s", separating "micro" and "organisms."
Ask these questions:
- What does micro mean?
- What are organisms?
- So, what are microorganisms? How small do you think they are?
Continue by asking these questions:
- What do you think microorganisms need to survive?
- Where do they live?
- Are microorganisms in our food?
- Are the microorganisms in our food harmful or helpful, or both?
Tell students that although not all microorganisms in food cause people to get sick, some do and that will be the focus of the lesson.
Have students access the What's Bugging You? student esheet and work individually or in small groups to complete it.
The first part of the esheet requires students to do a lot of reading, which can be done online or with print copies. It will be important for you to structure this reading to meet the needs of your particular students. For example:
- You could break the reading into chunks and stop to ask questions along the way to check for understanding.
- You could develop a worksheet that requires students to answer specific questions as they are reading and/or take notes, whichever they find most helpful.
- You could assign different groups to read different sections of the reading, eventually bringing the groups together to "teach" each other about what they read.
Listed below are sample answers to the guiding questions included on the esheet (students can write answers to these questions on the What's Bugging You? student sheet):
- What is foodborne illness? (A disease transmitted to humans by food.)
- What sorts of foods are "hotbeds" for foodborne pathogens? Why? (Moist, high-protein and/or low acid foods; these foods can support rapid growth of infectious or disease-causing microorganisms.)
- Who is at highest risk for foodborne illnesses? Why? (Elderly people, infants, unborn fetuses, and people with weakened immune systems may not have strong enough body systems to ward off foodborne illness.)
- How do foods become contaminated?(Chemically, such as by cleaning supplies getting into food; physically, such as by pieces of glass getting into food; and biologically, for example microorganisms growing in food.)
Continue the discussion of microorganisms by asking how microorganisms could cause contamination. Have students come up with cross-contamination scenarios; e.g., making meatballs with raw hamburger then touching lettuce for a fresh salad with unwashed hands. Follow this with more of the guiding questions:
- What are the four main types of microorganisms? (They are viruses, parasites, fungi, and bacteria.)
- What type of microorganism is the greatest threat to food safety? (Bacteria.)
- Name some foods that "good" bacteria are used to make. (Cheeses, buttermilk, sauerkraut, pickles, yogurt.)
- Under what conditions do bacteria thrive?(Warm, moist, protein-rich environments. Ask students to discuss scenarios that would create environments for bacteria to grow; e.g., milk left out on a counter [the milk is protein-rich and would get warm].)
- What is the most important thing you can do to prevent foodborne illness? (Practice good personal hygiene, including washing your hands.)
Assess student understanding by their participation in class discussions as well as their performance on the Lesson One: What's Bugging You? Achievement Test.
In addition, you could have students make flyers that promote the prevention of foodborne illness. The flyers should be creative yet based on the science learned in the lesson. Students could choose to address one of the following three topics, as they're related to foodborne illness:
Students should demonstrate an understanding that storing food at proper temperatures can prevent spoilage. One example of a flyer would be one titled "Refrigerate Food"; the flyer would explain that because bacteria like to grow in warm, moist conditions, foods should be stored in cool temperatures to prevent the growth of bacteria (particularly high-protein foods like milk and eggs).
Students should demonstrate an understanding of the importance of hand washing. They should explain why hand washing is important in the prevention of foodborne illness, as well as give examples of what can happen when this is not done.
Students should demonstrate an understanding of cross-contamination and give examples of how this can happen (e.g., when hands touch raw meat that has bacteria on it, and then touch other foods, like salad that will not be cooked).
Consider developing a rubric for assessment of the flyers. There are several resources on the Internet that describe the use of rubrics in the K-12 classroom, a few of which are highlighted here.
To learn more about rubrics in general, see Make Room for Rubrics on the Scholastic site.
For specific examples of rubrics, more information, and links to other resources, check out the following sites:
- Kathy Schrock’s Guide to Everything: Assessment and Rubrics
- Assessment: Creating Rubrics
- Rubrics for Web Lessons
Finally, you can go to Teacher Rubric Makers on the Teach-nology.com website to create your own rubrics. At this site, you can fill out forms to create rubrics suitable for your particular students and then print them instantly from your computer.
Follow this lesson with the second Science NetLinks lesson in the series, Microbes 2: Louis Pasteur–a Microbe Discoverer.
To extend the ideas in this lesson, see the Science NetLinks lesson Sanitation and Human Health.
To learn more about food safety, continue with Lessons 2, 3, and 4 at the Iowa State University: University Extension Food Safety Project site used in this lesson.
What's the most unsanitary spot in your house?, a one-page article, is directly related to the content of this lesson.
For a general introduction to microbes as well as more detailed information, visit the American Society for Microbiology's site, Microbe World.