Wallemia sebi

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A Microbial Biorealm page on the genus Wallemia sebi

Classification

Higher order taxa

Domain (Fungi); Phylum (Basidiomycota); Class (Wallemiomycetes); Order (Wallemiales); Family (Wallemiacea); Genus (Wallemia)

Species

Species (Sebi)

Wallemia Sebi

wallemia sebi reproduction (scale bar is 5um)

Description and significance

[3] W. sebi is one of three Wallemia species which are distinguished based on the size of the conidia formed and the extent of xerophily. It is an asexual fungus that reproduces through conidiogenesis. Its unique mode of conidiogenesis along with its strong ability to thrive without water are what sets Wallemia apart from other Basidiomycota.

Genome structure

[1] W. sebi has a compact genome (9.8 Mb), with few repeats and the largest fraction of genes with functional domains compared with other Basidiomycota. [1] The genome has been completely sequenced to aid in the understanding of W. Sebi’s biology and ecology.

Cell and colony structure

[2] Forms small, raised aggregates that are tan in color. Colonies grow best at 24˚C and [3] are very slow growing, reaching diameters between 3-6mm in 14 days. [2]The conidia produced mitotically; each is an exact replica of the parent. They are cylindrical and measure between 1.5-2.5 lm in diameter.

Metabolism

[2] Though little is known about its mode of fueling, W. Sebi is osmophilic which means that it prefers areas of high salt or sugar concentrations. All fungi are heterotrophic and most are facultative anaerobes, so it is highly likely that W. sebi is as well.

Ecology

[2] W. Sebi is found in dry habitats like wood, hay, textiles, in crawl spaces, mattresses and human skin. It is among the most xerotolerant fungi, and because it can grow at water activity below .85, it is considered xerophilic. Water activity (aw) is the unit of measurement used to describe the amount of water an organism requires for growth. It is this property of fungi that causes dehydrated foods to become moldy, as many mold causing fungi are xerophilic.

Pathology

[2] W. Sebi has been found to cause hay fever symptoms which include coughing, sneezing, itchy and watery eyes, itchy nose, and sinus pressure. W. Sebi has on rare occasions colonized human abscesses. There is one documented case of W. Sebi infecting an ulcer on the foot of a patient in northern India. The patient was treated with an antifungal, itraconazole, but the patient neglected to attend follow up appointments so it is unknown if the treatment was successful. [3]

References

[1] http://www.ncbi.nlm.nih.gov/pubmed/22326418; 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. The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction. Fungal Genet Biol. 2012 Mar;49(3):217-26. doi: 10.1016/j.fgb.2012.01.007.

[2] http://web.bf.uni-lj.si/bi/biologija-mikroorganizmov/Publikacije/PDF%20datoteke/2005_ZdHSFGC.pdf.; Polona Zalar, G. Sybren de Hoog, Hans-Josef Schroers, John Michael Frank and Nina Gunde-Cimerman. Taxonomy and phylogeny of the xerophilic genus Wallemia (Wallemiomycetes and Wallemiales, cl. et ord. nov.). Antonie van Leeuwenhoek (2005) 87:311–328

[3] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2268330/; Guarro, J., H. C. Gugnani, N. Sood, R. Batra, E. Mayayo, J. Gene, and S. Kakkar. "Subcutaneous Phaeohyphomycosis Caused by Wallemia Sebi in an Immunocompetent Host." Journal of Clinical Microbiology 46.3 (2008): 1129-131. Web. 27 Apr. 2013.



Edited by Kyla Clark, student of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio