Introduction to Fungi

Amanita Muscaria

• Fungi are  decomposers of organic material, they recycle chemical nutrients. They are highly diverse heterotrophs that act as detritivores.
• They are vital for the survival of most ecosystems, largely because  decomposition releases nutrients and makes them available for reuse by plants. 
• Fungi have mutualistic partnerships with plants,  making possible the sharing and efficient use of nutrients and the survival of both partners. 
• Fungi are generally heterotrophic uni- or multi-cellular saprotrophs, which obtain carbon through breakdown and absorption of surrounding materials. 

• The substructure of multicellular fungi takes the form of many chitinous microscopic strands, or hyphae; these may further subdivide into cells or form a syncytium containing many eukaryotic nuclei. 

• Fruiting bodies, of which mushrooms are the most familiar example, are the reproductive structures of fungi.

• About 100,000 species of fungi are currently known, though some 1.5 million species likely exist. 

• The majority of fungi are unicellular or filamentous. As fungi grow, they produce an intertwined mass of delicate threads that branch freely and often fuse together.

• Fungal forms vary, and the most commonly known resemble mushrooms or form spongy creeping growths. 

• While individual, tubular threads are called hyphae, a mass of threads is called a mycelium.

• Structures like mushrooms consist of many filaments packed tightly together.

• The surface-to-volume ratio of fungus is very high, ensuring that no part of the fungus is more than a few micrometers away from its environment. 

• Specialized hyphae, known as rhizoids, anchor some forms of fungus to the substrate. 
• Parasitic fungi have specialized hyphae known as haustoria, which anchor the fungus and facilitate the absorption of nutrients from the cells of other organisms. 
• Fungi are nonmotile and lack flagella or cilia, and environmental dispersal occurs during reproduction.
• Fungi such as mushrooms and truffles have long served as a direct food source, and fungi have often been used in the leavening of bread and the fermentation  of wine, beer, soy sauce, and other food products. 
• Since the 1940s, fungi have played a role in the production of antibiotics; more recently, various fungi-generated enzymes have been used in detergents and other industrial products. 

• Fungi are also frequently used as biological pesticides that control weeds, plant diseases, and insect pests.

• Many fungal species produce bioactive compounds called mycotoxins; these include alkaloids and polyketides, which are toxic to human and non-human animals.

• The fruiting structures of several species of fungi contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies. 
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• Fungi can break down manufactured materials and buildings, and they often represent significant human and animal pathogens. 
• Food spoilage and the loss of crops due to fungal disease (e.g., rice blast disease) can seriously impact human food supplies and local economies.

Vocabulary 

Heterotroph. An organism deriving its nutritional requirements from complex organic substances. 

Detritivore. An animal that feeds on dead organic material, esp. plant detritus.

Saprotroph. An organism that lives off of dead or decaying organic material.

Mushroom. Any of the fleshy fruiting bodies of fungi typically produced above ground on soil or on their food sources (such as decaying wood).

Hypha. A hypha (plural hyphae) is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.