Population Explosion
Bacteria are one kind of microbe. They are microscopic plant-like organisms that can be found everywhere on our planet, living in almost every possible environment. In this exploration students use mathematics to calculate bacterial growth.
Materials Required:
• Graph paper
• Calculator
Procedure:
1. Watch a video of bacterial division to start this exploration:
2. Bacteria reproduce by a process called fission. They split apart when conditions are right. Consider eating food that has been left out of the refrigerator for some hours. Is this a problem?
4. If temperature and humidity are favorable, and if there is good nutrition present, bacteria will multiply about every 12 minutes. How many bacteria will be present after a few hours based on one dividing into two, two into four, four into eight and so forth every twelve minutes.
5. Create a graph to track the growth of the bacteria. Plot the number of bacteria over time.
6. Analyze the graphs and report how many bacteria are predicted after 2 hours. What happens if you leave food out longer than that?
Questions
• Bacteria make byproducts when they consume food. What could be the problem with eating food with that byproduct?
• Why does refrigeration help stop the development of bacteria?
Discussion
The most common food poisoning bacteria are: Staphylococcus aureus, Salmonella, Clostridium perfringens, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus, Bacillus cereus, and Escherichia coli. Most of these bacteria are present in the environment and can come into food even though precautions are taken to keep things clean. When one or two bacteria are present it may not cause a problem. But, if they are allowed to grow, the toxins they make and the problems they can cause are dangerous for humans.
