Wallemia sebi

Wallemia sebi
Wallemia sebi colonies
Scientific classification
Kingdom: Fungi
Division: Basidiomycota
Subdivision: Agaricomycotina
Class: Wallemiomycetes
Order: Wallemiales
Family: Wallemiaceae
Genus: Wallemia
Species: W. sebi
Binomial name
Wallemia sebi

Wallemia sebi is a brown mold or hyphomycete commonly found in indoor air dust, soil and dried and salty foods (bread, cakes, sugar, dried fish, dates, bacon, jams). It is xerophilic, meaning it thrives in arid environments or substrates with little free water. To isolate this fungus, media with low water activity need to be used, with solutes such as glycerol, high sugar content or high salt content. It is present in a significant proportion of human dwellings.

On agar media with low water activity, W. sebi forms slow growing brown colonies with a fine velvety texture. The conidia (asexual spores) are produced in long chains derived from a conidiogenous cell on branches of hyphae, and are often in groups of four. Only the asexual stage is observed in culture, although analyses of its genome indicate the presence of mating genes and genes involved in meiosis.[1] Under salty conditions, W. sebi produces secondary metabolites causing hemolysis.[2] It has been rarely reported to cause subcutaneous infections in humans.[3]

References

  1. Padamsee M, Kumar TK, Riley R, Binder M, Boyd A, Calvo AM, Furukawa K, Hesse C, Hohmann S, James TY, LaButti K, Lapidus A, Lindquist E, Lucas S, Miller K, Shantappa S, Grigoriev IV, Hibbett DS, McLaughlin DJ, Spatafora JW, Aime MC. (2012). "The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction)". Fungal Genet Biol 49 (3): 217–226. doi:10.1016/j.fgb.2012.01.007. PMID 22326418.
  2. Botic T, Kuncic MK, Sepcic K, Knez Z, Gunde-Cimerman N. (2012). "Salt induces biosynthesis of hemolytically active compounds in the xerotolerant food borne fungus Wallemia sebi)". FEMS Microbiol Lett 326: 40–46. doi:10.1111/j.1574-6968.2011.02428.x.
  3. Guarro J, Gugnani HC, Sood N, Batra R, Mayayo E, Gene J, Kakkar S. (2008). "Subcutaneous phaeohyphomycosis caused by Wallemia sebi in an immunocompetent host)". J Clin Microbiol 46: 1129–1131. doi:10.1128/jcm.01920-07.
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