Bacteria, Microbes and Germs….Oh my! Objective: The objective of this lesson is to introduce the students to the concept of microorganisms. In this lesson they will learn what microorganisms are and how they can positively and negatively affect human health. For upper level students (3rd through 5th) this lesson will also reinforce their learning of the scientific method. Colorado Department of Education Standards http://www.cde.state.co.us/scripts/allstandards/COStandards.asp?stid=3&glid=3&stid2=3&glid2=0 Comprehensive Health Standard 2: Physical and Personal Wellness in Health ● Kindergarten: Expectation 2 -­‐ Explain how personal hygiene and cleanliness affect wellness ● 1st Grade: Expectation 2 -­‐ Demonstrate health enhancing behaviors to prevent unintentional injury or illness Science Standard 2: Life Sciences ● 1st Grade: Expectation 2 -­‐ An organism is a living thing that has physical characteristics to help it survive ● 2nd Grade: Expectation 1 -­‐ Organisms depend on their habitat's nonliving parts to satisfy their needs ● 3rd Grade: Expectation 1 -­‐ The duration and timing of life cycle events such as reproduction and longevity vary across organisms and species ● 4th Grade: Expectation 3 -­‐ There is interaction and interdependence between and among living and nonliving components of ecosystems Estimated Time: 1 or 2-­‐45 minute lesson periods. Materials: Basic Activity ○ Glitter (edible or not). Possible glitter that shows in a black light. ○ Vaseline Advanced Activity ○ Nutrient Agar Media kit (can be purchased from Carolina Scientific – Item #821045) ○ Hand sanitizer and/or soap ○ Bleach ○ Antimicrobial wipes Page 1 of 6
Background The microbial world is the most diverse of any group of animals on the planet. This is evident if you look at the tree of life below, which can be found at: http://microbialgenomics.energy.gov/primer/tree.shtml. As you can see below, there are three branches for plants, animals and fungi, and all the rest are microorganisms. There are many different types of microorganisms and they can be found basically everywhere! Some live in extreme environments such as deep in the subsurface of the earth, near volcanoes, and in extremely cold places like Antarctica. Some actually live inside our bodies and help us stay healthy, but some make us sick. When we talk about “germs” in human health we usually mean two very different types of microorganisms: viruses and bacteria. • The key “germs” or, more properly, microorganisms that create common illnesses are called viruses. Viruses constitute many of the “germs” that make students sick throughout the year (flu, colds, chicken pox, etc.). • Another key “germ” comes from bacteria (one of three domains of life that have microorganisms). • You can show the students the different types of “germs” that make them sick using images or props such as those found at giantmicrobes.com Page 2 of 6
Cold virus – Rhinovirus Bacteria that causes Strep Throat-­‐ Streptococcus Definitions: Microorganisms – An organism of microscopic size that cannot be seen with the naked eye. Bacteria are usually 2 micrometers or less: a micrometer is 1/1,000,000th of a meter!! Bacteria -­‐ One domain of life in the microbial world. Most of the microorganisms that cause human disease or live within the human body are in this domain. Germs – Bacteria, viruses and other microorganisms that cause, specifically human, diseases. Pathogens – A bacteria or virus that specifically causes disease (a.k.a. the science word for germs) Viruses – viruses are considered simple microorganisms. They are much smaller that bacteria or other traditional microorganisms. There is still debate in science about whether viruses are “alive”. But they are the main component of most human diseases. Basic Activity Procedure (K-­‐ 2nd) : 1. Before the students enter the classroom apply Vaseline and glitter to common “germ” areas around the classroom. For example apply the “germs” on door handle, drinking fountain, pencils, certain areas of their desks, and so on. 2. Go about the day as usual so that the students have a chance to come into contact with a lot of the “germ” areas. 3. During the science lesson. Discuss microorganisms with the students. a. Ask the students what they know about germs? Do they know what they look like? Page 3 of 6
b. Do they know any other names for germs (usually they are familiar with bacteria or bugs)? Discuss viruses, microorganisms and any other term they do not know. c. Talk about good microbes versus bad microbes. Ask why do we wash our hands? Why does that keep the bad germs from making us sick? i. Return to the discussion about how microbes can be found everywhere and the have them look at their hands and glitter…. ii. You can talk about antibiotics, hand sanitizer and soap as things that kill microorganisms, especially the bad ones. Advanced Activity Procedure (3rd through 5th) 1. Discuss microorganisms with the students. Ask them what do they know about germs? • What do they look like? • Where are they found? • What are other names for germs? • Are they all bad? 2. Review the basics about the microbial world • Show them the tree of life and explain where plants and animals are and that all the rest are microbes!! • Discuss some of the extreme places microbes can be found (see references). • Discuss the difference between good bacteria and bad bacteria. Especially those that make humans sick. 3. Now that the students have a basic understanding and/or interest: tell them we are going to do two experiments to learn about microorganisms, where they live and why things like soap and hand sanitizer work to keep bad bacteria from making us sick. 4. Safety in the Classroom – before starting these experiments, please read the following safety recommendations for working with microbes and media in the classroom. • It is important that the students never open the petri dish, as there will be live bacterial colonies present that contain millions of bacteria. Please explain this to the students and it may be helpful to place the dish in a Ziploc bag or put parafilm around the dish to ensure no one opens it, • The students and the teacher should always wash their hands before and after the experiment. It would also be good to keep hand sanitizer on each table for students to use as needed. • When the experiment is complete – put a small amount of bleach in each petri dish, then place them is a Ziploc bag container and throw them in an outside garbage bin. The bleach will kill most of the bacterial colonies. • When the exercise is completed, make sure to wipe down all the tables and other surfaces with antibacterial wipes. Page 4 of 6
5. Experiment 1 a. Have the students hypothesize where microbes in the classroom can be found. b. Now have them hypothesize where the MOST microbes might be found in the classroom. c. Work with the students to write a class hypothesis for both a & b. d. Split the students into groups and give them cotton swabs. Have them take “samples” of the microbes in each of the test sites. e. They can then swipe the cotton swab onto the nutrient media in the petri dish. There should be 1 petri dish per site/per group. Be sure not to push too hard when swiping the swab on the agar in the dish. f. Place the petri dishes someplace where they will get warm (in the sun) and grow them over night. g. Allow the students to observe the microbes as they grow. Explain to them that the bacteria are reproducing and making millions of copies of themselves. This will turn into things they can see on the plate called “colonies? h. After about 1-­‐2 days. Have the students count the number of colonies they see. And put total number in a group spreadsheet like the example. i. After compiling the classroom data, discuss with the students what the data tells them about their hypothesis. Was it correct? Why? Groups
1
2
3
4
5
6
Average
Loc A:
Door
Knob
Loc B:
Trash Can
Loc C:
Toilet
Seat
Loc D:
Water
Fountain
6. Experiment 2 a. In their groups, have the students elect one member to be the “test subject” b. Have the test student wipe their hands on the tables, doorknobs and other places that microbes may be. Then swab the student’s hand with a cotton swab and brush it on a petri dish. c. Then, have the student use hand sanitizer. After their hands are dry, swab their hands again with a new cotton swab and swipe cotton swab on a new petri dish. d. Allow the dishes to grow like in experiment #1. Then allow the students to look at them e. What happened? Discuss the results with the students. Page 5 of 6
References 1. Carolina Scientific -­‐
http://www.carolina.com/product/long+life+medium+kit+nutrient+agar.do 2. Giant Microbes.com -­‐ http://www.giantmicrobes.com/ 3. Microbes at NASA -­‐ http://microbes.arc.nasa.gov/ 4. Biology for kids -­‐ http://www.biology4kids.com/files/micro_main.html 5. Tree of Life -­‐ http://microbialgenomics.energy.gov/primer/tree.shtml Adams 50 Standards • SC.00.05.01.01 Identifies the common needs such as food, air, and water of familiar living things. (CMCS) (CAS Pr.2.2a) • SC.01.12.02.03 An organism is a living thing that has physical characteristics to help it survive (CAS: 1.2.2) • SC.01.22.01.03 Organisms depend on their habitat's nonliving parts to satisfy their needs (CAS: 2.2.1) • SC.01.42.03.03 There is an interaction and interdependence between and among living and nonliving components of systems (CAS: 4.2.3) • SC.02.12.02.03 An organism is a living thing that has physical characteristics to help it survive (CAS: 1.2.2) • SC.02.22.01.03 Organisms depend on their habitat's nonliving parts to satisfy their needs (CAS: 2.2.1) • SC.02.32.01.03 The duration and timing of life cycle events such as reproduction and longevity vary across organisms and species (CAS: 3.2.1) • SC.02.42.03.03 There is an interaction and interdependence between and among living and nonliving components of systems (CAS: 4.2.3) • SC.03.32.01.03 The duration and timing of life cycle events such as reproduction and longevity vary across organisms and species (CAS: 3.2.1) • SC.03.42.03.03 There is an interaction and interdependence between and among living and nonliving components of systems (CAS: 4.2.3) • SC.04.42.03.03 There is an interaction and interdependence between and among living and nonliving components of systems (CAS: 4.2.3) • SC.04.62.01.03 Changes in environmental conditions can affect the survival of individual organisms, populations, and entire species (CAS: 6.2.1) • SC.04.62.02.03 Organisms interact with each other and their environment in various ways to create a flow of energy and cycling of matter in an ecosystem (CAS: 6.2.2) • SC.04.82.01.03 Human activities can deliberately or inadvertently alter ecosystems and their resiliency (CAS: 8.2.1) Created by: Daniel Moran, Paul Martin and Kennda Lynch Page 6 of 6