Molds

Molds (including mushrooms) usually start with the germination of a spore (conidium) which sends out an elongated filament from its tip. This filament is the basic structure of growing molds is called a hypha. Many branches of hyphae are formed. Masses of them are called mycelium. Some hyphae grow above a surface and look like branches of a plant. These are called aerial hyphae or aerial mycelia. Other hyphae grow into the surface to absorb nutrients, much like the roots of plants do to gain their nutrients. These are called vegetative hyphae. Many nuclei are contained within the hyphae; and, in many species, crosswalls called septa are located at frequent intervals along the hyphae. Molds reproduce by developing spores (conidia) on the aerial hyphae. These spores act as seeds for new colonies of molds. A typical mold colony is able to produce many reproductive structures, which, in turn, may produce hundreds of spores that are easily scattered into the air. Certain fungal species are able to grow as either a yeast or a filament form. This trait is called dimorphism. Under certain conditions, the yeast form will develop. Under other conditions, the filamentous form is produced.

Bluish colored molds are usually from Penicillum spores. Mucor produces grey-colored mold. Neurospora, causing red spores, is a genus of mold common to bread. Neurospora is also capable of converting tryptophan to niacin, and is used in genetic and enzyme research.

Aspergillus is a genus of fungi producing molds from which several species become parasitic pathogens. Aspergillosis is the disease produced, causing infections seen most often in the immunocompromised individual. Respiratory infections with lesions containing masses of mycelia develop on the skin, in the lungs or bronchi, the ear canal, sinuses, or subcutaneous tissue, and sometimes involving the bones and meninges. In the very immunodepressed patient (as those with AIDS, leukemia, or Hodgkin’s disease), systemic aspergillosis often occurs and treatment is not always successful.