Mold

The colloquial term mold (or mould; see spelling differences) is applied to a large and taxonomically diverse number of fungal species where their growth results in a moldy appearance of objects, especially food. The objects become discolored by a layer of fungal growth. Molds are fungi that grow in the form of multicellular filaments called hyphae. A connected network of these tubular branching hyphae, called a mycelium, is considered a single organism. The hyphae are generally transparent, so the mycelium appears like very fine, fluffy white threads over the surface. Cross-walls (septa) may delimit connected compartments along the hyphae, each containing one or multiple, genetically identical nuclei. The dusty texture of many molds is caused by profuse numbers of asexual spores conidia formed by differentiation at the ends of hyphae. The mode of formation and shape of these spores is traditionally used to classify the mold fungi. Many of these spores are colored, making the fungus much more obvious to the human eye at this stage in its life-cycle. In contrast, fungi that can adopt a single celled growth habit are called yeasts.

Molds are considered to be microbes and do not form a specific taxonomic or phylogenetic grouping, but can be found in the divisions Zygomycota and Ascomycota. In the past, most molds were classified within the Deuteromycota. Molds cause biodegradation of natural materials, that can be unwanted when it becomes food spoilage or damage to property. They also play important roles in biotechnology and food science in the production of various foods, beverages, antibiotics, pharmaceuticals and enzymes. Some diseases of animals and humans can be caused by molds, usually as a result of allergic sensitivity to their spores or caused by toxic compounds produced as molds grow.