Wallemia sebi

Wallemia sebi is a xerophilic fungus of the phylum Basidiomycota.

It is commonly found on highly sugared or salted materials, such as jams, bread, cakes, sugar, bacon, salted meats, and salted fish. It is also found in indoor air, house dust, and soil.

One distinctive feature of W. sebi is its relationship with water activity. Most fungi are profoundly affected by the availability of water. The ability to tolerate environments with low water activity has been found mostly in Ascomycota, but rarely in Basidiomycota. However, W. sebi. can adjust its morphology and physiology to adapt to different environmental conditions and survive osmotic stress. Wallemia sebi have lower limits for growth below water activity of 0.75 (0.69-0.75)aw, while most microorganisms are limited to 0.95 and above.

Wallemia sebi has been isolated from hair, hay, textiles and man. It can grow slowly without additional solute in the growth medium, and form small, reddish-brown, powdery colonies.