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Any of the 200,000 or so of single or multiple cell organisms (living structures), microscopic (visible only using a microscope for magnification) and macroscopic (visible to the unaided eye), that are abundant in the natural environment.
Yeasts are single-cell fungi that live in colonies; molds are multiple-cell fungi that form structures. Like bacteria, fungi are among the oldest life forms to inhabit the Earth; fossils of yeasts date back more than 2 billion years.
Most fungi are harmless to humans and many are normal flora (present in body and on the skin). Fungi break down organic waste; yeasts, for example, populate the gastrointestinal tract where they aid in digestion. Many antibiotic medications derive from fungi, notably penicillin (first cultivated from the mold Penicillium chrysogenum).
Some fungi are pathogenic (disease causing) in people under any circumstances and others cause opportunistic infection in people who are immunocompromised. Fungal diseases may be localized, such as onychomycosis (fungal infection of the nail beds), or systemic, such as histoplasmosis. doctors use antifungal medications to treat fungal infections that cause disease.
|tinea capitis (ringworm)||tinea corporis (ringworm)|
|sporotrichosis||tinea barbae (ringworm)|
|tinea cruris (jock itch)||tinea pedis (athlete’s foot)|
Fungi may also be a source of poisoning. Aspergillus molds on grains produce aflatoxins, for example, which cause liver damage and are associated with liver cancer. Many types of mushrooms produce toxins (mycotoxins) that cause illness or death when eaten, such as the highly toxic “death cap” mushroom, Amanita phalloides.
Molds may grow in buildings where humidity and darkness converge to provide the ideal environment for their growth, such as inside walls and floors where there have been water leaks. The spores of these fungi cause respiratory illnesses and other health problems when breathed in with the air, particularly for people who have asthma or other chronic pulmonary conditions.
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