Hobbies And Interests
Laboratory Equipment
Experiments to grow bacteria require a variety of laboratory equipment and safety procedures. Common equipment includes sterile swabs, Petri dishes containing agar, parafilm, microscopes and glass slides. More advanced experiments may require Bunsen burners, inoculating loops and incubators. Safety and preparation is important when handling bacteria in the laboratory. Make sure students understand how to properly sterilize equipment before and after conducting experiments.
Designing an Experiment
Discuss different types of bacteria in the natural environment and how microbes grow on surfaces. Encourage students to design multiple experiments to compare different types of bacteria. Explain the importance of studying bacteria, including how scientists conduct experiments to study food safety and research new antibiotics.
Collecting Bacteria Samples
Bacteria samples are available commercially or can be collected by students as part of the experiment. Instruct younger students to collect samples in the classroom and around the school. Encourage older students to design experiments to compare the results of known and unknown bacteria samples and collect bacteria from multiple sources.
Growing Bacteria
For a simple experiment, instruct students to take a sample using a single sterile swab and spread it thoroughly over an agar-filled Petri dish. More complicated experiments can be designed for older high school and college students using a two-step process. In the first step, students use the streak plate method to spread out and isolate bacteria colonies. In the second step, students spread selected bacteria onto designated portions of a Petri dish using an inoculating loop. After spreading bacteria on a Petri dish, students should seal it with parafilm to limit airborne exposure of the bacteria and keep the agar from drying out.
Evaluating Results
After students have finished growing bacteria, it is ready to examine under a microscope. Instruct students to prepare bacteria samples on glass slides and view them under a microscope. Compare the results with photographs of known bacteria and direct students to prepare laboratory reports explaining the results.
Proper Cleanup and Disposal
Instruct students to safely dispose of used agar plates by adding a tablespoon of bleach to the plate before placing it in a biohazard bag. Teach students to clean their hands properly after handling bacteria and laboratory equipment. Talk to students about the importance of hand washing to stop the spread of germs.