NAME OF LESSON: Bacteria is EVERYWHERE!

Subject Area: Biology (microbiology, biology of organisms)

Age or Grade: Middle school

Estimated Length: 3-4 classes

Prerequisite knowledge/skills:

Students can do this activity at the beginning of the school year, after learning how to use a basic microscope and learning about the properties of living things and single-celled organisms.

Description of New Content:

Bacteria is everywhere! Some is good, some is bad. Use of antibiotics and antiseptics, bacterial resistance.

Goals:

Students will investigate the question “where can we find bacteria?” by swabbing various areas of the school and streaking a nutrient agar plate. They will observe and sketch their colonies for several days under the microscope, and meanwhile will learn via slide presentations about different types of common bacteria – some good and some bad. Students will also test the effects of various different disinfectants on the growth of their colonies. Students will understand the usefulness and drawbacks of antibiotic use.

Materials Needed:

Nutrient agar plates, marked into quadrants with wax pens (these plates can be bought already poured, or poured yourself using sterile technique - nutrient agar from chemical supply company comes with directions)

Sterile swabs

Various disinfectants (ethanol, Lysol, dish soap, etc)

Sources of GOOD bacteria (yogurt, for example)

Microscopes

Computer with LCD projector and internet access to view online photos of various bacteria.

Procedure:

Each student should receive an agar plate with four quadrants drawn on it, plus 4 sterile swabs to take samples from anyplace they choose. The students should record where they swabbed in their lab journal. Plates should be stored at room temperature and observed daily. Its helpful for the teacher to also make a plate with GOOD bacteria on it, such as from a swab of yogurt.

Opener:

Ask students – where in this room can we find bacteria? Have them brainstorm and ask probing questions, like “how about the air? Your body? The water from the water fountain?”

Development:

After students have brainstormed, and possibly predicted that bacteria can be found anywhere and everywhere, ask them how this could be tested. Then explain how agar plates work (ie: what is agar and how is it made?) and have students plan out good uses for the four quadrants on their plate in their lab notebooks. Demonstrate sterile technique for swabbing, then set students free to investigate!

Closure:

Plates should be checked daily for a few days, and on day 3 or so try adding various disinfectants to test bacterial growth. Students can look at plates under microscopes and write lab reports on their findings, including drawings or graphs for their counts of colonies. At the conclusion, make sure students can answer these questions: What is bacteria? Where can bacteria be found? What areas did you swab? Which grew more bacteria? Did the bacteria look different for any area you swabbed? Can you tell if this is good or bad bacteria by looking at it? How should plates be properly disposed and why? How did the disinfectants affect the growth of your colonies?

Evaluation:

Lab report, graphs, drawings, thinking questions.

Extensions: N/A

References:

Bacteria

http://www.bacteriamuseum.org/

http://www.ucmp.berkeley.edu/bacteria/bacteria.html

http://commtechlab.msu.edu/sites/dlc-me/

http://www.microbeworld.org/

Pouring agar plates:

http://www.sciencebuddies.org/mentoring/project_ideas/MicroBio_Agar.shtml

Pathogenic bacteria