Often referred to as germs and thought of as harmful, bacteria are all around us. They are an inescapable part of life on Earth. Amazingly, there are more bacterial cells in our bodies than our own cells!
Bacteria have simplified cellular structures and lack the nucleus and membrane-bound organelles of Eukaryotic cells. Bacteria are usually divided into two kingdoms, Archaebacteria and Eubacteria. Archea are fascinating examples of the adaptability of life. They live in extreme environments, such as the hot acid springs of Yellowstone National Park, sea floor vents, and deep underground. An enzyme present in a thermophilic species of Archea has been used to develop the polymerase chain reaction technique that is now a cornerstone of molecular biology. The amazing survival abilities of these bacteria have given scientists a renewed perspective on where life may exist.
Eubacteria are the ‘true bacteria’ that include those that we are most familiar with. They are classified by their shape and proteins embedded in their cell walls. Cocci are spherical, Spirilla are spiral-shaped, and Bacilli are rod-shaped. In fact, students can practice using Latin roots with bacterial names. For example, the prefix staphylo- means in clusters, so Staphylobacillus bacteria are rod-shaped and grow in clusters. The commonly known Streptococcus bacteria grow in chains (strepto-) and are spherical. In addition to teaching the usage of Latin roots, bacteria provide ample opportunity to explore many other biological concepts. For example, antibiotic resistant bacteria show evolution in action.
When teaching about bacteria, I love to have students culture the microbes on petri plates. I still remember doing this as a high school student. A plain nutrient agar can be purchased from most science supply companies. While the pre-made plates are convenient, making your own is simple and much more economical. I like to buy the bottled agar that you can heat and pour, which is really simple and foolproof. You can use sterilized inoculating loops or swabs to collect bacteria from surfaces around the classroom and school. My students pair up and determine two surfaces to test. I have them hypothesize which surface will contain the most bacteria. This gives us another opportunity to practice the scientific method. For safety’s sake, I have the students seal the plates with tape after they have inoculated them. Then we place the plates in an incubator. We check the plates daily and after a few days you should see some interesting cultures. Place the used plates in a biohazard bag or autoclave them to ensure that harmful bacteria do not find their way out.
Harmful bacteria are frightening, but there are just as many helpful bacteria. Have your students do research on both a harmful bacterium and a helpful one. They can then present their findings. Strep throat, tuberculosis, tetanus, and pneumonia are all caused by species of bacteria. Of course, most bacteria are harmless, with some helping make yogurt and tofu, and others helping us digest food and remain disease-free. Students could make ‘Wanted’ posters with their bacteria, some being wanted for crimes and others being wanted to help humans.
The following lessons will also help your students learn all about these ‘bugs’ of the microbe world.
Bacteria Lessons and Activities:
Students examine a variety of environmental and industrial roles of bacteria. They explore where bacteria can be found and distinguish bacteria from other organisms.
Students examine the existence of bacteria all around them and consider the roles, both positive and negative, that bacteria play. Over a period of several days, students conduct an experiment in which they predict, determine, log, and evaluate samples.
Students monitor and study bacterial growth. In this bacteria study lesson, students observe bacteria over one week and calculate the rate of growth. Students calculate surface area, draw graphs, and approximate bacteria and nanobe populations.
Students examine where bacteria grows, how it grows and why it grows. They explore how oftentimes bacteria grows most in areas that look clean, and the least in areas that look dirty. They study agar and grow their own selection of bacteria collected from certain areas on school grounds.
Students are able to name one kind of harmful bacteria and why it hurts us and also name one kind of helpful bacteria and how we use it. They describe the process of growing bacterial cultures in a lab. Students create a reasonable hypothesis, recognize whether the experiment data supports or disproves their hypothesis, and draw conclusions based on their lab findings. They define a control and its contribution to an experiment.
Students identify the different Eubacteria phyla. They comprehend the biology of bacteria, genetics associated with bacteria and pathogenic bacteria. Students complete a bacteria "wanted" poster assignment. They discuss the notes over Eubacteria phyla.