Allergenic fungus (Alternaria alternata), SEM

Coloured scanning electron micrograph (SEM) of the sporulating, filamentous fungus Alternaria alternata. Filamentous hyphae are seen here producing conidiophores with conidia at their tips. Alternaria is a dematiaceous (phaeoid; black pigmented mould) fungus commonly isolated from plants, soil, food, and indoor building environments. These moulds are characterized by their dark pigmentation due to melanin, which absorbs harmful UV-radiation. They are causative agents of phaeohyphomycosis and other respiratory allergies. It is the most common species isolated from human infections. Cases of onychomycosis, sinusitis, ulcerated cutaneous infections, and keratitis, as well as visceral infections and osteomyelitis have been reported. Alternaria alternata also causes leaf spots, rots and blights in plants. Magnification: x400 when shortest axis printed at 25 millimetres.