Science Fair Projects With Mold & a Petri Dish

Bread Mold Project

• Wet a piece of bread, and place it in a plastic container and let it sit for five days. Examine it every day, and when you can see circles or spots of mold growing on it, it is ready to be placed on a petri dish. Scrape the tip of a sterile petri dish inoculation needle along one circle of mold of a single color to pick up some of the mold. Scrape the mold off the needle onto the petri dish medium, in the shape of an "E." Scrape off a sample from each different-colored mold spot on the bread; place it in a seperate petri dish. Label the petri dishes with masking tape and a felt-tipped pen. Let them sit in a dark, warm place at 77 degrees Fahrenheit for five days. Use a sterile inoculation needle and scrape off the center of a seperate circle of mold in the petri dish, then place it on a new petri dish. Repeat with the other mold samples in the petri dishes; let them sit another five days. Place the pure mold colonies that you grew in the second set of petri dishes on wet mount slides and observe them under a microscope. Each mold will have its own shape, color and appearance.

Mold Growing Contest

• Make four different petri dish mediums out of starch and gelatin mixture or starchy foods such as potatoes, bananas and oatmeal; boil the medium for 10 minutes to sterilize it. Place it into four different petri dishes, and let them sit for 30 minutes. Put on the petri dish lids and label them with masking tape and a felt-tipped pen. Put each petri dish into its own zip-lock plastic bag; let the petri dishes sit in a warm, dark place in your house. Look at the food every day, and write down any changes you see in it over the course of a week. Don't open the container or the zip-lock plastic bag; just observe it through the clear plastic of the container. Make a chart for each day and each food type. Each day, take pictures of the contents of the dishes to use in your science fair display.

Grow Slime Mold

• Slime molds are a single-celled organism that grows in colonies that take on the form of a slime. Some slime molds can actually move across forest floors, which makes them an interesting science fair project. Slime mold, or physarum, is sold in a small square or filter paper culture. Place the filter paper in a non-nutrient petri dish, and add the slime mold culture to it. Place a flake of oatmeal on the culture. Cover it and set it in a dark room for 12 hours. Every 12 hours, add one to two oatmeal flakes to make the slime mold grow. Observe the slime mold. As it starts to multiply, you will see it take on a slime-like mass. Grow other slime molds in petri dishes and use the first one as your control for your experiments. You could experiment by seeing how slime mold grows in different temperatures.

Test Disinfectants

• Grow molds in petri dishes as described in Steps 1, 2 and 3, and then add small amounts of different types of disinfectants, such as hand sanitizer and soaps. Observe how the chemical substances affect the mold. Do they stop additional mold growth or kill off the colony entirely?