- 8 wide plastic food containers with lids
- 4 packets of gelatin
- 2 teaspoons sugar
- 1 cup canned chicken or beef broth
- 1.5 cups water
- 1 bulb of garlic
- Garlic press
- 8 cotton balls
- Distilled water
- Permanent marker
- Choose three areas where you’ll use your swabs to collect microbial life. You can choose anything that you think might have microbes on it. For example, you might swab the door handle because a lot of people touch it, or the kitchen counter before it’s been washed. There are many places that microbes like to hang out.
- Gather your eight food containers and make sure that they are clean (fresh out of the dish washer is best!). Label two of them with the name of the first location you swabbed, two of them with the name of the second location, two of them with the name of the third location, and two of them as Control. Remember—what’s a control, and why is it important?
- Let’s create some munchies for the microbes! First, put the gelatin, the sugar, water, and broth into a pot on the stove.
- Bring the mixture to a boil while stirring with the spoon. Make sure everything has dissolved.
- Remove the mixture from the heat and wait until it stops boiling.
- Divide the microbe food into two bowls. Use your garlic press to press four gloves of garlic and use the spoon to mix this into one of the bowls.
- Use the funnel to place an equal amount of microbe food in each food container. You’ll want the gelatin in each container to be about half an inch deep. One of the food containers in each pair will contain microbe food with garlic, and the other will contain microbe food without garlic.
- One the food is in the food container and the lid is on tight, let the gelatin set (cool and harden).
- Now, add your microbes! Dampen eight cotton balls with the distilled water and take two samples from each location. Gently swipe the microbe-laden cotton ball across the surface of the gelatin in your first food container, then collect another sample from the same location and do the same with the second container (the one that contains the garlic). Make sure not to break the surface of your gelatin as you do this!
- Repeat step 8 for all the microbe locations you want to test, and make sure all of your food containers are appropriately labeled.
- For your control containers, simply dampen and swipe the cotton balls across the surface of each gelatin mixture without adding more microbes.
- After you’re finished with all of the containers, wait! It may take a few days for the microbes to really get going. Observe each of the containers daily and make notes about what you see. Do the containers that contain garlic get the same amount of microbial flora as the containers that don’t contain any garlic? Why or why not?
- When you’ve finished the experiment, throw away the containers without opening them, since they contain large amounts of different microbial populations. Some might be dangerous!
The microbes will grow best in the containers that do not contain garlic.
In this experiment, you gave microbes some food and watched them grow. But what is a microbe? Microbes are tiny, single-celled organisms that include bacteria, fungi, and protists. They are so small that millions of them could fit onto the head of a needle, but they still pack a big punch: microbes can cause diseases like cholera. They can also be incredibly helpful. Lots of important bacteria live inside your body and help you with bodily processes such as digestion.
Alright, so how is garlic related to the growth of microorganisms? While humans have created medicines that work against certain microorganisms to help treat diseases, many plants have developed natural anti-microbial properties, including garlic. While some of the human medicines work against very specific microorganisms, garlic is antibacterial, antifungal, antiparasitic, antiprotozoan and antiviral. It’s a micro-organism-fighting superstar!
Try the experiment again, only this time, use garlic powder. Do you think that this will work more or less effectively against the growth of microorganisms?