Growing Airborne Molds
Students will learn that the spores in the air produce visible mold colonies when provided with nutrients and moisture.
Students will expose petri dishes containing a nutrient agar to the atmosphere (outdoors or even indoors) for a short period of time. The dish is then covered and sealed. Students will check the dish daily for the appearance of mold colonies. It will take approximately four to seven days for colonies to develop. Students will be able to count the number of colonies and probably even see that there are different types of fungi.
Fungal spores are present in the atmosphere year round, especially on warm, sunny, and windy days. These spores develop from fungi growing in the environment on many different substrates. They are most common in the soil and on decaying vegetation. Most of these fungi are part of the natural recycling that occurs in nature, although some may be plant pathogens as well. These fungi are easy to grow in culture. We will be growing the fungi in petri dishes that contain Malt Extract Agar. Agar is a gelatin-like material that is used in the study of bacteria and fungi. Nutrients are added to the agar, and it is steam sterilized and poured into these plates. Like gelatin it solidifies when it cools. Fungi are able to absorb the nutrients and the moisture in the agar as they are growing.
Many of these same fungi are introduced indoors through open doors and windows and also on our shoes and clothing when we enter a building. Indoors, many of these fungi find a suitable habitat. Nutrients and moisture are often abundant indoors. We often find these molds growing in bathrooms on shower curtain and walls. We find them growing on foods in our refrigerator. They also grow in carpeting, in basements, and in attics. Spores of many of these common fungi are known to be important allergens. These can act as triggers for rhinitis (hay fever) or asthma.
The major purpose of this activity is for students to increase their awareness of what is actually in the air. Although the air may look clear there may be many spores in the air. These spores will give rise to visible mold colonies when provided with a source of nutrients and moisture.
Mold colonies from an air sample