Parasitic Fungi

Parasitic Fungi


or pathogenic fungi, fungi that use as a source of food live tissues of various organisms. Parasitic fungi cause diseases in plants, animals, and humans.

Many parasitic fungi are members of the class Fungi imperfecti, since they reproduce only asexually. The body of a parasitic fungus consists of branching multicellular filaments (hyphae) of the mycelium. Parasitic fungi form spores of various sizes and shapes. Obligate parasitic fungi feed only at the expense of live tissues, and, as a rule, do not grow in artificial nutritional media. Among the facultative parasitic fungi, some feed predominantly on organic substances of decaying tissues (saprophytes) but can also parasitize live tissues; other saprophytes are usually parasitic but can also grow on dead tissue.

There are parasitic fungi that live on animals and are called zoopathogenic fungi, which include entomopathogenic fungi, which live on insects. Parasitic fungi that live on plants are called phytopathogenic fungi and include mycophthorous fungi—that is, those that live on mushrooms. Phytopathogenic fungi are the most common. They act by means of toxic secretions or enzymes, which damage plant tissue, and then use these tissues as food. Many of the phytopathogenic fungi attack economically valuable plants. For example, various rust fungi cause stem rust and brown rust of grasses (Puccinia graminis, P. triticina), sunflower rust (P. helianthi), and flax rust (Melampsora lini); smut fungi cause durum and powdery wheat smut (Tilletia tritici, Ustilago tritici); and powdery mildew fungi cause powdery mildew of grasses (Erysiphe graminis). Parasitic fungi cause apple scab (Venturia inaequales), grape mildew (Plasmopara vitícola), and many other diseases. There is a large well-known group of wood-destroying fungi that grows on living trees (various species of Polyporaceae and honey fungus), as well as on commercial wood and wooden parts of buildings (house fungi). Fungous plant parasites are combated by means of special agricultural techniques, the production of hardy varieties, and the application of chemical substances (disinfection of seeds, spraying of plants, etc.). Mycophthorous fungi parasitize the fruit bodies and mycelia of many other fungi.

Zoopathogenic fungi include those that cause ringworm, favus, and other diseases of the skin of mammals and humans. Malassezia furfur causes furfur, and fungi from the genus Epidermophyton cause epidermophytosis of the feet and groin. Parasitic fungi from the genera Candida and Geo-trichum cause mycoses of the mucous membranes, skin, nails, and other areas. Parasitic fungi from the genera Blastomyces, Sporotrichum, and Aspergillus attack not only the skin but also subcutaneous cell tissues, muscles, bones, and the internal organs of animals and humans. Under certain conditions (for example, when the natural bacterial flora in the human organism are suppressed by excessive use of antibiotics) some parasitic fungi can cause a systemic disease in the organism, for instance, candidiasis.

Entomopathogenic fungi are used for exterminating harmful insects. The best known are Empusa muscae, a parasite of house flies; E. grilly, a parasite of locusts; and Beauveria bassiana, which parasitizes many insect species.


References in periodicals archive ?
Asexual reproduction as a success model seems to be characteristic of many parasitic fungi, including those that afflict humans, such as athlete's foot.
There is also much to say for organic farming as it is well known that pesticides and parasitic fungi have worsened the decline of the vital honeybee.
Specific topics include slow-down of oceanic carbon dioxide uptake in response to global warming, mycosporine-like amino acids in phytoplankton, the impact of parasitic fungi on the diversity and functional ecology of marine phytoplankton, and bio-mitigation and biofuel production using microalgae.
These are two types of parasitic fungi and one type of parasitic nematode, or roundworm.
Life-forms such as the flying colugo, red crab spiders, blue birds of paradise and the parasitic fungi cordyceps, which have developed unique survival abilities, are also observed.
Dermatophytes, parasitic fungi that affect skin, hair or nails, are the primary agents that cause onychomycosis.
Unlike other fungicides, which often contain toxic active ingredients that kill plant parasitic fungi by poisoning them, SafeScience's ELEXA complex carbohydrate formula contains no toxins.
Yet these human mediations are often as integral to the whole as are Rockman's parasitic fungi, strangling vines, the carnage left by rapacious predators.
The ability of some plant parasitic fungi to produce extracellular pectinases in culture has been related to their pathogenic activities (Cleveland and McCormick, 1987; Crawford and Kolattukudy, 1987; Reyes et al.
Itraconazole is active against parasitic fungi like the kind that infects the toenails.
From parasitic fungi to sculptures made entirely out of hair, this book is sure to shock, intrigue and confuse even the most level-headed of us.