What Are Fungi?
Fungi (singular: fungus) are eukaryotic organisms that belong to the kingdom of Fungi, in addition to animals, plants, monera, and protozoa. Fungi are diverse in nature, occurring in various forms, the most common forms being molds, yeast, mushrooms, and truffles. Fungi are mostly microscopic. They consist of thread-like structures with a diameter of less than 10 m and are called hyphae. These structures grow into mycelium, which is a vegetative mass. Mycelium acts to absorb nutrients from the environment and does not rely on photosynthesis.
Collage of different types of fungi
Types of Fungi
Fungi are classified into five types of phyla: Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycota, and Zygomycota.
Ascomycota are also called sac fungi, which have a sac-like structure called an ascus. In the sexual stage, the ascus contains 4-8 ascospores. The sac fungi are divided into subgroups, (i) based on whether the asci are single or are borne in fruiting structures called ascocarps, and (ii) based on the discharge method of the ascospores. Ascomycetes are mostly plant pathogens; some ascomycetes are animal pathogens; a few of them occur as mushrooms that are edible; and many ascomycetes occur as saprobes that live on dead/organic matter. Morels and truffles constitute the most commonly known and largest ascomycetes.
Photo of Ascomycota fungi
The phylum Basidiomycota is the second largest. It comprises 35,000 species and is divided into three main groups: Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina. The members of Basidiomycota are filamentous, the exception being Basidiomycota, which has yeast-like forms. Members of the Basidiomycota have club-shaped cells called basidia. Specialized sexual spores produced by basidia are called basidiospores.
Schematic of different parts of Basidiomycota fungi
The Chytridiomycota phylum comprises chytrids that are aerobic and zoosporic fungi. They are found in the form of saprotrophs and pathogens in brackish, freshwater, and marine habitats and are also found in abundance in soil. There are two pathogenic species: Synchytrium endobioticum, which is the cause of wart disease in potatoes; and Batrachochytrium dendrobatidis, which causes chytridiomycosis in amphibians. The Chytridiomycota phylum produces uniflagellate zoospores, which do not form colonies but produce spheroidal bodies called thalli. These species absorb nutrients from their environment. They are transformed into sporangia, which release zoospores when there are insufficient nutrients.
Photo of Chytridiomycota fungi
The Glomeromycota phylum is newly established, comprising 230 species that are found to be closely associated with the roots of plants and trees. Most members of the Glomeromycota phylum form arbuscular mycorrhizae. The hyphae form a mutually beneficial association with the root cells: the plants supply energy and carbohydrates to the fungi, which in turn supply essential minerals to the plants. This mutual association is called biotrophic. The Glomeromycota species can also be found in wetlands and salt marshes.
Microscopic image of Glomeromycota fungi
In the fungi kingdom, the Zygomycota phylum comprises a relatively small group of zygomycetes. They include Rhizopus stolonifer, which is the familiar bread mold. They rapidly propagate on the surfaces of fruits, bread, and vegetables. They are mostly terrestrial habitats and live on plants and animals or in soil. Most species are called saprobes, and thus find decaying organic material. Some are parasites living in insects, plants, and small animals, and some form symbiotic relationships with plants. The metabolic products of Rhizopus are used as intermediates in the synthesis of semisynthetic steroid hormones.
These fungi reproduce asexually and produce sporangiospores, which, when landing on a suitable substrate, germinate and produce a mycelium.
Schematic of Zygomycota fungi
Some of the Benefits of Fungi
- Fungi recycle 85% of carbon from dead organic matter. They release the nutrients that were locked up, which can be used by other organisms.
- Penicillin, derived from the fungus Penicillium, is a well-known antibiotic.
- Edible mushrooms contain a large amount of vitamin D2, which helps the human body absorb phosphorus and calcium.
- Fungi are used in the production of industrial chemicals, including lactic, citric, and malic acids.
- Fungi are used in bakeries for making bread and also for making beer and wine.
Some of the Disadvantages of Fungi
- Some molds produce mycotoxins, which are poisonous, and aflatoxin, which is a cancer-causing agent.
- The Tinea species causes ringworm that can affect the trunk, head, and extremities of the human body.
- However, inhalation of some fungal spores can affect several organs at once and may even result in death in people with compromised immune systems.
- Candida albicans, a yeast usually present in the esophagus, mouth, vagina, and bowel, causes infection when it overgrows.
- It was reported in 2012 that fungal disease and infection cause the destruction of approximately 125 tons of food crops annually.