Bread mold, commonly seen as a fuzzy growth on stale food, is a type of fungus, frequently identified in experiments as Rhizopus stolonifer. This organism is a saprophyte, meaning it obtains nutrients from non-living organic matter, such as the sugars and starches found in bread. Observing the growth cycle of this fungus provides a direct opportunity to study the fundamental principles of mycology and decomposition in a simple science experiment.
Essential Materials and Setup
To begin this investigation, you will need a slice of bread, a resealable plastic bag or clear airtight container, and a source of water (a clean spray bottle or dropper is best). While any bread will eventually mold, a plain white variety or one with fewer preservatives will show faster results. The sealable container acts as a miniature environment, which will be crucial for maintaining the high humidity necessary for fungal development.
The bread serves as the nutrient-rich substrate, providing the carbohydrates the mold requires for energy and structure. Using clean materials helps ensure that the growth you observe is primarily from airborne mold spores rather than existing contaminants. Gather all these items on a clean surface before starting to minimize extra variables in your setup.
Step-by-Step Cultivation Instructions
The first step is to introduce moisture to the bread without soaking the slice completely. Lightly spritz the surface two to three times, or use a dropper to place about ten drops across the surface. The goal is to create a damp surface, not a soggy one, as excessive water can inhibit mold growth.
Once the bread is properly moistened, carefully place it inside the plastic bag or container, avoiding contact with the inner surfaces. Seal the container completely, ensuring the enclosure is airtight to trap the moisture inside. This preparation creates an environment where naturally-present mold spores can begin their life cycle.
Creating the Optimal Growth Environment
Mold spores require a specific combination of warmth and moisture to germinate successfully. The optimal temperature range for Rhizopus stolonifer growth is between 25° Celsius and 30° Celsius (77°F–86°F), making a consistently warm location ideal. The sealed bag traps water vapor, creating the high humidity required for airborne spores to swell and begin producing hyphae.
The bread provides a steady supply of carbon and nitrogen, which the fungus absorbs as nutrients through its growing network of filaments, called the mycelium. Placing the sealed container in a dark or dimly lit area is preferred because it mimics the natural decomposition environment of fungi. Within three to five days, the mycelium will become visible as a cottony white mass before developing characteristic colored spores, such as the black sporangia of Rhizopus.
Safe Handling and Observation
Once the experiment is set up, the most important safety rule is to never open the sealed container once mold growth is visible. Mold spores released by mature colonies can become airborne and act as respiratory irritants, especially for people with allergies or asthma. All observations of the growing mold must be conducted through the clear plastic barrier.
Observe and record the chronological changes, noting the first appearance of the white mycelium, followed by the development of colored spore-producing structures. The colors can vary, with black, green, or blue-green patches commonly appearing depending on the specific species of mold present. When the observation period is complete, dispose of the sealed container directly into the trash without opening it to contain the spores. After disposal, you should thoroughly wash your hands with soap and water.