The fascinating world of fungi

Some of the most interesting science is in your kitchen! You can find a fascinating variety of life: mold, yeast, and mushrooms, all grouped together as fungi. In this article we’ll look at ways you can find out more about these organisms. For any experiment, there’s a key that can be really helpful. Have you heard of the scientific method? Basically, you start with a question, like “what happens to this if I add that?” Then based on what you read about a topic, come up with a hypothesis, a prediction of what you expect to happen in certain conditions. Next, you can experiment to find out if your hypothesis is right! For the most accurate results, you need to control the experiment’s variables (for a mold-growing project like these, include type of bread, room temperature, and amount of light). Be sure to use at least one “normal” piece as your control, so you have a standard for comparison.

Once you’ve completed the experimentation stage, look at your predictions again. Do you need to do more research and change anything, based on your results?
What Are Fungi?
There are five “kingdoms” of living organisms: plants, animals, fungi, and tiny bacteria and protozoa. Mushrooms, molds, and yeasts are all in the fungi kingdom. Although sometimes they look similar to plants, fungi do not produce their own food through photosynthesis. Fungi range in size from just one tiny cell to several inches tall. Fungi are important decomposers, eating up dead leaves and other rotting organic material. Unlike when you eat and your food is digested (broken down into tiny parts) inside your body, fungi digest their food outside of their bodies and then absorb it into their cells. Fungi have many different means of reproduction, but all are able to reproduce by forming spores, which are spread out and develop into more fungi.

Many fungi are harmful, causing diseases like athlete’s foot and Dutch elm disease (in trees). But some fungi can also be used for saving lives. Perhaps the greatest use of fungi is in the treatment of bacterial diseases that used to be deadly, such as scarlet fever and pneumonia. Starting in the late 1920s, scientists discovered that a type of mold, Penicillium notatum, prevented the growth of some bacteria. They created an effective antibiotic, called penicillin, to treat bacterial diseases. As you know if you’ve ever left bread or fruit on the counter for too long, mold is easy to grow! This is because mold produces a lot of spores and they spread easily. All you need to grow mold is 1-2 pieces of bread and some scraps like fruit peels, carrot shavings, or coffee grounds. 

Mold needs light and oxygen to grow. They also do best at room temperature. Based on what you’ve found out about mold, what do you expect to be the best environment in your house for growing it? What about the worst? How do you think heat and cold will affect growth?
As you experiment with mold, follow these safety rules! Do not touch mold or bacterial growth with bare hands. (Use gloves if you want to touch the mold.) Be sure to wash your hands with soap and water after holding a moldy specimen, even if you don’t touch the mold directly. In this experiment you’ll compare mold growth on bread and on other food at the same time. First, get four pieces of bread (or divide two in half). Splash each of the pieces with water to dampen but not soak them. Place each piece in an individual plastic bag. Don’t seal the bags completely, so some air can still get inside. Now place two of the bags in a spot where they will get some sunlight. Place the other two in a spot where they will get less light, but the temperature is about the same as in the other spot.

Next, put the food scraps (either all the same kind or a mixture) on two paper plates. Set one next to the first set of bread specimens and the other next to the bread in the darker spot. After 2-4 days you should see some spots of mold growing. Mold spores grow on stalks, kind of like mushrooms but on a smaller scale. These raised spores are what give mold on food a fuzzy appearance. Mold is usually blackish on starchy foods like bread, and a fuzzier blue or green on fruit. Wait a couple more days until there’s a large area of mold on the food. Which set of bread has the most growth on it, the one in the light or the one in the dark? What about the scraps? Do some scraps have more mold than others?
As you discuss what you see, you might also want to write down your observations and make sketches. Use a magnifying glass or a microscope, if you have one, to look at the mold spores close up. What do you see? (To view under a microscope, use a sharp knife to carefully scoop up some of the mold and set it on a microscope slide. Look at the mold under low and then high power.)

For further study, come up with your own experiments that help answer the following questions: Which foods are most susceptible to mold, ones high in starch or high in protein? What difference does the presence of sugars make? If mold grows best in a slightly acidic environment (5-6 pH), how might you make it grow faster? Think about what foods are more acidic; for instance, vinegar and lemon juice are highly acidic at 2-3 pH, while apples have an acidity of 3-4 pH.