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Common mold, or fungi, appears in our world as a fuzzy, cobweb-like growth over organic matter. Molds reproduce by making spores, tiny, lightweight fragments that can become airborne. Mold and mildew are commonly used interchangeably, although the term mold is often applied to black, blue, green, and red fungal growths, and mildew to whitish growths. Black bread mold (Aspergillus), one of the most familiar molds, begins as a microscopic, airborne spore that germinates on contact with the moist surface of the nonliving organic matter.
The most common types of mold are Cladosporium, Penicillium, Aspergillus, and Alternaria. In our normal environments, people are exposed to molds everyday without adverse health effects. They help to challenge our body’s natural protection system so we can develop natural antibodies and maintain our health against various maladies. Problems occur with individuals where systems are over challenged or where the natural system is compromised.
Fossil records suggest that molds and fungi were present 550 million years ago and may have evolved even earlier. They range from tiny, single-celled organisms invisible to the naked eye to some of the largest living multicellular organisms. In Michigan for example, the underground portion of an individual Armillaria mushroom, a type of fungus, extends more than 30 acres. Other fungi are among the longest-lived organisms on Earth; some lichens have a living partnership of fungus and algae, and are thought to be more than 4,500 years old.
Mold spreads rapidly, forming the mycelium (fungal body), which is made up of a fine network of filaments (hyphae). The mycelium produces other clusters of root like hyphae, called rhizoids, which penetrate the organic material, secreting enzymes and absorbing water and the digested sugars and starches. Other clusters of hyphae called sporangiophores then reach upward, forming sporangia (knoblike spore cases), which bear the particular color of the mold species. Upon ripening, the sporangia break open and the windborne spores land elsewhere to reproduce asexually. Some molds also reproduce sexually through conjugation of gamete cells by the joining of two specialized hyphae. The resulting zygote matures into a zygospore that germinates after a dormant period. It is primarily the airborne spores that can create an uncomfortable environment.
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