Deuteromycetes are an artificial group of fungi, of which there exist approximately fifteen thousand species, often referred to as “fungi imperfecti” because their only known reproductive mechanism is asexual.

Deuteromycetes—also known as Deuteromycota, Deuteromycotina, fungi imperfecti, and mitosporic fungi—are fungi that are unable to produce sexual spores and are therefore placed in their own separate phylum. The deuteromycetes are commonly called fungi imperfecti, that is, “imperfect fungi,” a term accepted by many mycologists.


Reproduction in the deuteromycetes occurs in several different forms. Spores, or conidia, may be produced directly on the mycelium (the mass of hyphae, or tubular filaments, forming the body of a fungus) or on a structure of specialized mycelial cell called a condiophore.

Some of these fungi do not produce spores. Nonsporulating fungi are able to propagate themselves by fragmenting the hyphae or by producing a mass of hyphae called a sclerotium. Sclerotia can be microscopic in size or as large as several millimeters in diameter.

Conidia can vary in size and shape from small (2-3 microns long) to large (250-300 microns long). Colors can range from clear (hyaline) to a variety of earth tones. Conidia may consist of one to several cells. Shapes of conidia range from simple and oval to elongated and filamentous.


Classification of the fungi as deuteromycetes is based on the presence of conidia; the kind of conidia according to their shape, color, and size; and whether the conidia are produced in fungal structures called conidiomata.

Conidiomata may have the shape of a flask made of fungal tissue, called a pycnidium; a pin cushion, called a sporodochium; oramass of conidiophores located under either the epidermis or the cuticle of a plant host, called an aecervulus.

There are three classes. The hyphomycetes contain the fungi that produce conidia and conidiophores on hyphae or groups of hyphae. The agonomycetes do not produce conidia. The coelomycetes contain the fungi that produce conidia in distinct conidiomata.

Economic and Research Uses

The fungi in the deuteromycetes are extremely important for humanity. Several members of the deuteromycetes are used in industry. Antibiotics, such as penicillin and griseofulvin, are produced by these fungi, especially those of the genus Penicillium.

These fungi are often found in the soil, and it is believed that they produce antibiotic substances in order to reduce competition with soil bacteria and other fungi.

Penicillium fungi

Enzymes are produced by many of these fungi to enable them to degrade plant residues, from which they obtain nutrients. The enzymes they produce have been used by humans in the manufacture of laundry detergent, paper, and condiments such as soy sauce; the enzymes have also been used in scientific experiments. These enzymes are easily produced under industrial conditions.

Some of the fungi in the genus Penicillium are also used in the production of cheeses, including blue cheese and brie. After the cheese is processed and formed into wheels, spores of the fungus are injected into blue cheese, and cheese wheels of brie are dipped into a solution of spores. The cheeses are then allowed to age before entering the market.

Deuteromycetes as Pathogens

Several thousand species of deuteromycetes are pathogenic to plants and plant parts. Many are responsible for the degradation of foods, including decay from rots and molds on grains, vegetables, and fruits.

Deuteromycetes as pathogens
Deuteromycetes as pathogens

All of the deuteromycetes, like other fungi, are heterotrophic (eat or get their food from other organisms) and therefore need to attach to an organic substrate (a living foundation). Food products are excellent substrates for fungi and, within short periods of time, the fungi will consume and destroy these foods.

Some fungi produce toxic chemicals that are harmful to those who eat the rotting food. One example is aflatoxin, which is produced by the fungus Aspergillus flavus, found on peanuts. A general screening for the fungus can be done using a black light, under which the fungus fluoresces a yellow-green color.

Because all plants and plant parts that serve as food sources for people are affected by deuteromycetes, diseases of plants and animals are one of the more important effects of this fungal group.

The fungi use their ability to produce enzymes to enter into growing plant tissues and then destroy the tissue. Annual crop losses caused by fungi in the United States can be measured in billions of dollars. In addition, the small spores of deuteromycetes can affect animals and humans directly.

The spores are released into air currents and are blown from place to place. As humans breathe this air, the spores enter the nasal passages and lungs and react with the immune system, creating the allergies.