Fungi are plant-like organisms. It has been estimated that there are about 1.5 million species of fungi but only about 100, 000 species have been fully described and for most of these, little is known about their biology. If we don’t know what they are, how do we know what they do?
Fungi have a tremendous history of use by human beings. Many types of mushrooms are eaten, for example button mushrooms and oyster mushrooms. Of course, there are also many species of mushrooms that are poisonous and are responsible for numerous cases of sickness and death every year. A type of single-celled fungus called yeast is used to bake bread and to ferment alcoholic beverages, while mycelial fungus is used to make certain types of sauces (soy sauce). They are also used to produce industrial chemicals such as lactic acid, antibiotics and even to make the once popular stonewashed jeans. Some types of fungi are ingested for their psychedelic properties, both recreationally as well as religiously.
Fungi are important as decomposers that break down dead organic matter, releasing inorganic nutrients. They are hosted in nearly 300,000 land plant species, with each plant hosting one or more of these fungi. Some are used as biological pesticides to control weeds, plant diseases and insect pests.
Fungi cannot make their food since they lack chlorophyll of higher plants and algae. They are recognized by their fruiting bodies, which are the visible part of the fungus. Examples include mushrooms, puffballs, molds, cup fungi, and morels. The vegetative structure consists of minute filamentous cells called hyphae, which are microscopic in size, usually from 1 micron to 10 microns in diameter. An aggregate of hyphae is called a mycelium.
Fungi that cause plant diseases impact on humans more than the ecosystems. Those that grow and break down manufactured buildings materials after moisture damage become significant health hazards of building occupants. Those that produce mycotoxins, such as aflatoxins, are harmful to birds, fish, humans, and other mammals.
Some fungi, called endophytes, live in a symbiotic relationship with plants that benefits both plant and fungus. These fungi are highly efficient at absorbing nutrients, while photosynthetic products from the plant are absorbed by the fungus. Fungi used to be classified in the Plant Kingdom but were later transferred to a Kingdom of their own, that is, the Fungi Kingdom Fungi, one of the five kingdoms of life. Fungi are classified into groups based on the shape of the spore-producing structures and on their ability to reproduce sexually.
With the exception of yeast, fungi are characterized with filamentous bodies, nonmotile sperm, cell walls made of chitin, and nuclear mitosis. Fungi are eukaryotic and heterotrophic. They have cell walls made of chitin, and they store carbohydrates as glycogen. Fungi are also different from either plants or animals in their cell division.
Fungi are perhaps the most unappreciated, under valued and unexplained organisms on earth. Fungi are chemoheterotrophic, mostly aerobic or facultatively anaerobic organisms. Fungi have a potential role in degradation of explosives and toxic compounds. Fungi are a major cause of wood degradation in buildings.
Some Fungi cause human, animal or plant diseases. Fungi can break down manufactured materials and buildings, and become significant pathogens of humans and other animals. Some species of Fungi produce highly potent toxins such as aflatoxin. Aflatoxins are potent toxins and carcinogens in food of birds, fish, humans, and other mammals.
Fungi are important in the manufacture of bread and alcohol and help flavor wine, cheese, and other foods.