Fungi

Fungi are a diverse group of organisms that obtain food by direct absorption of nutrients. Food is dissolved by enzymes that the fungi excrete and then absorbed through cell walls. Together with bacteria, fungi are responsible for the decay and decomposition of all organic matter and are found wherever other forms of life exist. Some are parasitic on living matter and cause serious plant and animal diseases Fungi were traditionally classified as a division of the plant kingdom. They were thought of as plants that have no stems or leaves and that in the course of becoming food absorbers lost the pigment chlorophyll. Most scientists today, however, view them as an entirely separate group that evolved from unpigmented flagellates and place them either in the protist kingdom or in their own kingdom, according to the complexity of organization.

REPRODUCTION AND CLASSIFICATION

Spores are usually formed in one of two ways. In one process the spores form after the union of two or more nuclei within a specialized cell or series of cells. These spores typically germinate into hyphae that have different combinations of the hereditary characteristics of the parent nuclei. The four types of spores that are produced in this way-oospores, zygospores, ascospores, and basidiospores-are representative of the four principal groups of fungi. Oospores are formed by sexual union of a male and a female cell, zygospores by conjugation of two similar sex cells. Ascospores are spores (usually eight) that are contained in sacs (asci), and basidiospores (usually four) are contained in clublike structures (basidia). Included among the 25,000 species of this group are the prized Morel and Truffle mushrooms

The other usual method of spore production involves the transformation of hyphae into numerous short segments or into various kinds of more complicated structures. Here, the fusion of two nuclei is not a requirement. The principal reproductive spores formed in this asexual manner include oidia, conidia, and sporangiospores. Sporangiospores are formed inside bladderlike containers called sporangia. Most fungi produce spores both sexually and asexually.

The Fifth group of Fungi are called "Imperfect Fungi"
Around 25,000 additional fungus species are grouped in this phylum -- these species are the "left-overs" that don't fit well into any of the other groups. Members include Athlete's foot, Penicillin, and "Yeast" infections.

USES OF FUNGI

The hydrolytic enzymes of fungi are useful for a number of industrial processes. When grown on steamed wheat bran or rice bran, one fungal species produces an amylase product useful in alcoholic fermentation. Proteases obtained from another fungus are used in the manufacture of liquid glue. Commercial production of industrial ethyl alcohol is accomplished by fermentation of sugarcane molasses or hydrolyzed starch by means of enzymes formed by another fungus. In the process of making bread, yeast is added to dough to produce carbon dioxide.

Fungus is used for the commercial production of citric acid and in the production of gluconic acid and of gallic acid, which is used in the manufacture of inks and dyes. Synthetic resins are manufactured from fumaric acid formed by black bread mold (right). Gibberellic acid, which promotes increased growth of plant cells, is formed by a fungus causing disease in rice plants. Commercially usable oils have been obtained from species of several genera, and one species is a practical source of edible proteins. Vitamin D is prepared by irradiation of ergosterol, a substance which may be obtained from the waste brewer's yeast. A yeastlike fungus is a source of riboflavin, and biotin accumulates during production of fumaric acid by another fungus. Fungi are also used to produce Roquefort cheese and to ripen Camembert cheese.

Fungi have been used medicinally since ancient times. The use of fungi as a purgative is no longer prevalent, but the alkaloid in the sclerotium of ergot still is used to produce uterine contractions in childbirth. Ergot alkaloids are also a source of lysergic acid diethylamide, commonly known as LSD, which produces hallucinogenic effects, often of a severe nature. The use of antibiotics (see Antibiotic) in medical practice dates from recognition of the antibiotic properties of penicillin. Many antibiotics today are produced by nonfungal microorganisms. Griseofulvin, however, is an antifungal antibiotic formed by several species of a genus of fungi. The immunosuppressant drugs cyclosporine and tacrolimus (FK-506), both used in organ transplantation, are also derived from fungi.

Penicillin is an important antibiotic derived from the mold Penicillum notatum, pictured here. Penicillin is effective against a wide range of disease-causing bacteria. It acts by killing bacteria directly or by inhibiting their growth.

Andrew McClenaghan/Science Source/Photo Researchers, Inc.

The plasmodial slime mold is a mucouslike plant that creeps along slowly in leaf litter or over decaying logs. Although slime molds are grouped together with plants, they are considered heterotrophic, amoeboid organisms; that is, they lack photosynthetic ability and must seek out foods that they can engulf and consume in an amoebalike fashion. These primitive organisms feed on bacteria, fungal spores, yeast cells, and decaying plant and animal matter.

M.P.L. Fogden/Oxford Scientific Films

Lichens are actually a combination of two entirely different types of living organisms, an alga and a fungus. This association is called a symbiotic relationship. In this particular type of symbiotic relationship neither partner can live independent of the other. Lichens are very slow growing and can survive very harsh environmental conditions and are ecologically significant in that they contribute to the weathering of solid rock.

G.I. Bernard/Oxford Scientific Films

Bread yeast, Saccharomyces cerevisiae, or baker's yeast, a type of fungi, reproduces by a process called budding. Bread yeast causes bread to rise by releasing carbon dioxide, which gets trapped in the dough. Here, microscopic yeast (left) have a macroscopic effect (right) on bread dough.

Michael A. McClure. PHD/Phototake NYC;Safra Nimrod/Phototake NYC

The edible pore mushroom, or penny bun, is typically found in open deciduous forests during the summer and early autumn months. Many other related mushroom species are also edible.
Oxford Scientific Films

The sulfur fungus is one of the largest of the edible fungi, reaching a width of several meters and a weight of several kilograms. It is also one of the most brilliantly colored of the fungi.
Oxford Scientific Films

For much more information go to:

http://www.perspective.com/nature/fungi/