Paecilomyces variotii

Paecilomyces variotii is a common environmental mold that is widespread in composts, soils and food products. It is known from substrates including food, indoor air, wood, soil and carpet dust. Paecilomyces variotii is the asexual state of Byssochlamys spectabilis, a member of the Phylum Ascomycota (Family Trichocomaceae). However, the Byssochlamys state is rarely observed in culture due to the heterothallic nature of this species (i.e., it requires culturing of positive and negative strains in co-culture to produce the teleomorph). Paecilomyces variotii is fast growing, producing powdery to suede-like in colonies that are yellow-brown or sand-colored. It is distinguishable from microscopically from similar microfungi, such as the biverticillate members of the genus Penicillium (affiliated with the genus Talaromyces) by its broadly ellipsoidal to lemon-shaped conidia, loosely branched conidiophores and phialides with pointed tips. Ascospores of the sexual state, B. spectabilis, are strongly heat-resistant. As such, the fungus is a common contaminant of heat-treated foods and juices. It is also known from decaying wood and creosote-treated wood utility poles. Paecilomyces variotii has been associated with a number of infective diseases of humans and animals. It is also an important indoor environmental contaminant.