Microorganisms… in Space and on Earth Topic Microorganism Growth & Food Safety Key Question (s) How quickly do microorganisms multiply? How can you microorganism growth be managed to ensure safe food? Grade Level 6-8 Module Correlation Growing Space, Volume 3 (p. 8-9) Vocabulary Microorganism Bacteria Water Activity Organism Lesson Summary Through demonstration, students will learn about microorganisms and how quickly they reproduce. They will learn about microbes in space and transfer that information to practical ways they can keep their food safe here on Earth. Learning Goals Students will: 1. See the effect of microorganism multiplication on a piece of bread, 2. calculate the multiplication of microorganisms, 3. compare how microorganism growth is controlled in space travel and on Earth, and 4. discuss practical ways to maintain food safety. Science Competencies/Standards NSES Content Standard A, C, D Materials Needed Two Ziploc bags A sealed loaf of bread-you will only be using two pieces One pair of plastic gloves Jar full of 256 beans or dry pasta pieces Overhead Transparency of Microorganism Multiplication -Page B Overhead Transparency of Managing Microbes-Page C Overhead Transparency of Managing Bacteria and Other Microbes in our Food-Page D Background Information People have not and will not be able to go to space without taking trillions of microorganisms with them. Microorganisms are defined as any organism too small to be viewed by the unaided eye. Examples of microorganisms are; bacteria, protozoa, and some fungi and algae. An organism is a form of life composed of mutually interdependent parts that maintain various vital processes. Many microorganisms are harmless and some are even beneficial to humans. For example, the bacteria in our stomach produce vitamin K which is for proper blood clotting. There are others that aid in food digestion. People need these microorganisms. Harmful microorganisms are the ones NASA is working to control on the International Space Station. Unfortunately, current experiments are showing that some harmful microorganisms thrive under the conditions in space. These harmful microorganisms can pose a thereat to the materials and hardware in the Space Station. They can also make astronauts sick. Just as microorganism control is important in space, it is very important to people here on Earth. Bacteria growth in food can cause many food safety hazards. If harmful microorganisms are not controlled, food borne illnesses may result. One way to control microorganism growth is by controlling water activity in food. Water in food which is not bound to food molecules can control the growth of bacteria, yeasts, and molds. Water activity refers to this unbound water. Management 1. The teacher will want to do Procedure #1 approximately two weeks prior to the lesson. If it cannot be done that far in advance, the bread can be used a week or so after the lesson to revisit the topic of microorganisms and food safety. 2. Prior to the lesson, fill a jar with 256 pieces of something readily available in the classroom. Beans or dry pasta could be used. Only one jar of 256 pieces is needed. 3. The words microbe and microorganism are used in the lesson. They have the same meaning. Procedure Part One 1. Show students the loaf of bread. With gloves on, take one piece of bread out of the bag and quickly place it into a Ziploc bag. Seal the bag tightly and display it on the board. Take out a second piece of bread and have students pass the bread around the classroom. Tell them that they can touch it as much as they want. Once every student has touched the bread, place it back into the other Ziploc bag. Display it next to the other piece of bread. 2. The bread that has been touched by students will grow much more mold and fungi than the one you put directly into the Ziploc bag. As you study microorganisms and food safety, use the bread as a reminder of how important cleanliness is when working with and preparing food. The moldy bread shows that invisible microorganisms are everywhere-even on our hands. Part Two 3. As a class, read Invisible Astronauts from the SAITC module. Review with students that there are two types of microbes-beneficial and harmful. Tell them that for this lesson they will be focusing on the harmful microbes. These are the microbes that scientists are worried about. They must be controlled on the space station so that astronauts will remain healthy. 4. Ask students, “Who were the first inhabitants of the International Space Station?” From the article, they should answer that the first inhabitants were microbes. Ask students, “Why are astronauts worried about the microbes on the space station?” Remind them that harmful microbes could affect the hardware and materials of the Space Station and cause astronauts to become ill. 5. Show students the jar of 256 items. Tell them to pretend that the 256 beans (or other item) represent a bacterial colony made up of 256 single-celled bacteria. Ask them how many bacteria they think would have to be present to end up with the 256 in the jar. Tell them that the 256 resulted from only one bacterium. Ask them how long they think it took for one bacterium to multiply to 256. Explain that it only took 2 hours and 40 minutes to go from one bacterial to a total of 256. 6. Using a transparency of Multiplying Microbes-Page B, show students how bacteria multiply. Explain to students that they actually grow exponentially. This means that each cell divides into two cells. The two newly created cells have the same genetic material as the original cell. Each cell division takes only about 20 minutes. Part Three 7. Use a transparency of Managing Microbes-Page C to discuss with students the techniques NASA is trying to reduce microbe-related problems in space travel. Use a transparency of Managing Bacteria and Other Microbes in our Food-Page D to discuss ways to keep bacteria and other microorganisms from growing in food. Draw attention to the thermometer to show the proper temperature to store and cook food. Connecting Learning Use the following questions to guide a discussion on how students can control microorganism growth in their environments and at home. 1. What types of things should you consider when buying food at the grocery store? [buy food that is cold last and get it home quickly] 2. When you are not using perishable food, where is the safest place to keep it? Is it safer to thaw food on the counter or in the refrigerator? [in the refrigerator-it’s important to keep food between 32ºF and 40ºF in the refrigerator] 3. When cooking, what areas of the kitchen need to be kept especially clean? Why? [cutting boards, knives, countertops-if they are not kept clean, harmful microorganisms can be spread from food to counters and back to food] 4. Food borne illness often occurs at picnics. Why do you think people become sick from food eaten at picnics? [Picnic food often sits out for several hours without being refrigerated. Food maintains a temperature that encourages microorganism growth.] 5. What are proper ways to clean counters? [use hot water, antibacterial soaps and cleansers] Extensions 1. Have students act out the multiplication of bacteria. Start with one student who will then become two students. After the two students come up, branch two more students off of each one of them. This will demonstrate how quickly microorganisms multiply. 2. Introduce the concept of scientific notation to students using bacteria. Show how the 256 bacteria (demonstrated with the beans in a jar) would be expressed as 2.56 x 102 in scientific notation. 3. See “Microbe Activities” on Space Agriculture in the Classroom website for three additional experiments. Teacher Resources NASA Website-Microscopic Astronauts http://science.nasa.gov/headlines/y2004/23feb_yeastgap.htm This article gives a basic introduction to the study of microorganisms in space and experiments that are testing how microorganisms behave in space. NASA Website-Microscopic Stowaways on the ISS http://science.nasa.gov/headlines/y2000/ast26nov_1.htm This article provides information on microorganisms and how scientists are working to control their effects in space. NASA Website-Space: A Bad Influence on Microbes http://science.nasa.gov/headlines/y2003/01dec_yeast.htm This article describes an experiment which shows that the common food-borne pathogen Salmonella becomes more potent when grown in a microgravity environment. Reference Some lesson ideas were adapted by the work of the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture and The Pennsylvania State University.