Aspergillus ustus
From Wikipedia, the free encyclopedia
| Aspergillus ustus | |
|---|---|
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| Aspergillus ustus group colony on Modified Leonian's agar | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Eurotiomycetes |
| Order: | Eurotiales |
| Family: | Aspergillaceae |
| Genus: | Aspergillus |
| Species: | A. ustus |
| Binomial name | |
| Aspergillus ustus | |
| Synonyms | |
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Aspergillus ustus is a microfungus and member of the division Ascomycota. It is commonly found in indoor environments and soil.[1] Isolated cases of human infection resulting from A. ustus have been described; however the majority of these are nail infections.[2][3]
Morphology and physiology
Colonies of A. ustus appear dull brown sometimes with a purplish to grey brown or dark brown with a yellow to brown reverse side;[4][5][6] colonies are flat to furrowed often with a central bump.[6] Microscopically, the fungus is characterized by elongated conidial heads with bent Hülle cells scattered throughout the pigmented mycelium.[6] The conidia are rough-walled and spherical, ranging in color from green to yellow-brown.[6][7] The vesicles range from 7–15 μm in diameter and are hemispherical to almost round.[6] Although A. ustus is able to grow at human body temperature, other species in this group, such as A. baeticus and A. pseudoustus, require relatively low temperature for growth and thus are unlikely to cause human infection.[7]
Secondary metabolites
Despite that A. ustus has long been recognized as a common soil-associated fungus, knowledge of its biochemistry remained poor until recently. One of the first metabolites to be isolated and characterized from this fungus, ustic acid (C11H7O7), reacts with Iron (III) chloride to form a deep purple-colored compound. Ustic acid has since been shown to occur in other fungi, notably closely related Aspergilli such as A. granulosus and A. puniceus.[6] Aspergillus ustus produce a number of other metabolites including autocystins (and versicolourins), austalides, a sterigmatocystin-like chemical, and nidulol. Some metabolites of A. ustus have antibacterial properties.[4] Metabolite chemistry has been shown to be useful for the taxonomy and identification of this fungus.[6]
Phylogenetic position
Like other members of the genus Aspergillus, the A. ustus group is affiliated with the family Trichocomaceae. A phylogenetic study of Aspergillus section Usti using morphology, secondary metabolite chemistry and gene sequencing (beta-tubulin and calmodulin) revealed 21 distinct species and showed an affiliation of the section with two teleomorph genera, Emericella and Fennellia.[8]