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Nature Bulletin No. 638-A   April 23, 1977
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Mold is the common name for those cottony, cobwebby, or powdery growths that appear on almost any food, leather, cloth or paper stored in a dark, damp place. Soil, however, is the natural habitat for most of them. There they break down dead plant and animal materials and maintain the soil's fertility. From our standpoint, some are good, some bad.

Molds, along with bacteria, yeasts, mildews, blights, rusts, smuts and mushrooms make up that great subdivision of the plant kingdom called the Fungi. All of them lack the chlorophyll by which common green plants use the energy from sunlight to manufacture their own food. Instead, they get their nourishment from dead plant and animal remains, or as parasites on other living things.

Dry, dust-like mold spores -- of many different kinds and by the millions -- are carried by the wind and everything else that moves. They are on the ground, on trees, and on almost every square inch of our homes. A colony covering a whole slice of fresh bread can grow in a few days from a single microscopic spore. Under favorable conditions the spore swells, bursts its wall and sends out a short slender thread. This grows longer and branches into many threads. Some turn down like roots to absorb food. The tips of others turn upward to form tiny white globules which darken as they ripen. Then, each pops open to release thousands of new spores. In blue mold, chains of spores push out in clusters that resemble tiny tassels. Under a lens these mold colonies are exquisite fairy gardens.

Certain kinds of blue mold have long been used in making cheese to give distinctive qualities and flavors. The famous Roquefort cheese, so- named after a town in France where it is ripened in caves, is a white cheese made from the milk of sheep in which there are blue-green streaks due to sifting powdered bread mold into the curd. Gorgonzola cheese from Italy, and Stilton from England, are also mold-ripened. Our brown, salty soy sauce borrowed from China is prepared by a long slow fermentation of soy beans and rice with a mold.

Of the multitude of species of mold-like fungi, some cause infections and diseases in animals and man. Two of our skin diseases, more aggravating than dangerous, are ringworm and athlete's foot. Chickens eating moldy grain get a mold infection of their air sacs. In winter, fish are often killed by a water mold that produces patches of gray fuzz on their skins or gills.

One of the most revolutionary medical discoveries of all time was made in 1938 by Dr. Alexander Fleming of England. It started when one of the culture plates on which he was growing pathogenic bacteria was accidentally contaminated with a spot of blue mold. He noticed that the mold had created a bacteria-free ring around itself and was shrewd enough to realize what it meant. That was the origin of the antibiotic drug, penicillin. Since then, hundreds of other antibiotics, most of them produced by as many different molds, have their special uses in the control of bacterial infections in man and domestic animals.

About this same time, Dr. George W. Beadle, of the University of Chicago, used different strains of red bread mold which had been crippled by radiation to learn how the hereditary materials -- genes -- controlled growth. He showed that each gene produces its own enzyme or catalyst to do its work. Both he and Dr. Fleming were awarded Nobel prizes for their outstanding contributions to science.

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