Mold Library
Alternaria
Distribution
The genus Alternaria is found worldwide and in a variety of habitats. Alternaria species are ubiquitous agents of decay, commonly recovered from plant litter, sewage, paper, textiles, food and building materials. Some species may also act as plant pathogens. Alternaria is often recovered from water damaged buildings. Alternaria spores are dispersed by air currents and are frequently isolated from outdoor air.
Growth Characteristics
Alternaria grows rapidly. In culture, the colony is flat, downy to woolly, greenish black or olive brown with a light border and a brown to black reverse. On building materials, Alternaria growth appears as dark olive to black spotting or staining.
Microscopic Characteristics
Conidiophores are simple, septate and brown, occasionally having a zigzag appearance. Spores are produced in single or branched chains from the tips of the conidiophores. Spores are large, dark brown, and are divided into several cells by transverse and vertical walls. The end of the spore nearest the conidiophore is round and tapers towards the apex; this gives the Alternaria spore its characteristic beaked or club-like appearance.
Health Effects
Alternaria is a common allergen. Over 70 secondary metabolites of varying toxicity have been found to be produced by species of Alternaria; as such, the occurrence of Alternaria mycotoxins in foodstuffs is becoming an increasing concern. Although Alternaria is not generally considered pathogenic to humans, cases of opportunistic infections in immunocompromised patients (i.e. underlying autoimmune diseases such as AIDS or recent recipients of transplants) are becoming more common.