Wallemia sebi
| Wallemia sebi | |
|---|---|
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| Wallemia sebi colonies | |
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Wallemiomycetes |
| Order: | Wallemiales |
| Family: | Wallemiaceae |
| Genus: | Wallemia |
| Species: | W. sebi |
| Binomial name | |
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Wallemia sebi |
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| Synonyms | |
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Torula epizoa Corda(1829), Sporendonema sebi (1832), Sporendonema epizoum(1934) |
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Torula epizoa Corda(1829), Sporendonema sebi (1832), Sporendonema epizoum(1934)
Wallemia sebi is a xerophilc fungus of the phylum Basidiomycota.
It is commonly found on highly sugared or salted materials, such as jams, bread, cakes, sugar, bacon, salted meets, 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 tolerant 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.
Wallemia sebi is currently recognized as a species of the genus Wallemia, which is first introduced by Johan-Olsen in 1887 for a single species W.ichthyophaga Johan-Olsen. A large number of synonyms were used before it was classified in Wallemia, including Torula epizoa Corda, Sporendonema epizoum Corda, Sporendonema sebi Fr., and Sporotrichum navale Joly. The most commonly used synonyms is S. sebi, which was named to refer to the fact that the conidia are endospores. It was only until 1970, when von Arx synonymized Sporendonema with Wallemia, W.sebi is combined with S. sebi.
After a taxonomic revision in 2005 two other species were recognised in the genus, W. muriae (another xerophilic species) and the halophilic W. ichthyophaga.Wallemia sebi was distinguished from the other two in that it showed growth also on media without additional solutes, while W. ichthyophaga and W. muriae grow only in the present of additional solutes. In 2015 W. sebi was further split into W. sebi sensu stricto and three new species described as W. mellicola, W. canadensis, and W. tropicalis. The species differ in their conidial size, xerotolerance, halotolerance, chaotolerance, growth temperature regimes, extracellular enzyme activity profiles, and secondary metabolite patterns.
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