Mould is the substance seen on old vegetables or bread. It is a type of fungus that grows on moist or rotten matter. Black spots appearing on wet cloths kept undisturbed are concentrated collection of conidia produced by the fungi. In British English ‘mold’ represents the word ‘mould’. Conidia is an asexual reproductive body. Molds are normally microbes. There are many varieties of molds with diverse life styles.
Mold spores exist in the atmosphere and settle and grow when the conditions are conducive. Moisture is a pre-requisite for the growth of the fungus. Living mould is similar to mildew. A mould grows in the form of multicellular filaments called hyphae. Fungi that are grown in single celled format are classified as yeast. The hyphae are transparent, so the substance formed over the surface appears like very fine, fluffy white threads.
Presence of moisture in atmosphere creates a suitable environment for the growth of mold. Clothes made of cotton or other organic materials are a good platform for the growth of mildew and mould. Wet clothes along with dirt and human sweat act as good source of food for the fungi. Often an unpleasant odour is observed along with formation of the black spots. This odour is produced when human perspiration is converted by the fungi into foul smelling bodies such as amines, ammonia, fatty acids etc.
Mould often grows on moist cotton fabrics and fabrics made of other natural fibers. These materials are easily digestible by fungi and hence are more prone to attack in favorable conditions. However, it may be noted that moulds can grow on any material like book, carpet, furniture, bathroom tiles etc. Though synthetic fibers are more resistant, they are not completely immune to the attack.
Food preservation methods like salting, freezing, drying etc are used to reduce or prevent the growth of mold and other microbes. Presence of molds is essential for biodegradation and decomposition of natural materials, though it is often considered a disturbance. Some molds cause diseases in animals and humans. But, they are important in biotechnology and food technology. They find application in production of various foods, beverages, pharmaceuticals, antibiotics and enzymes.
It may be noted that slime molds and water molds are not fungi. What is a slime mold? What are their different types?