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

[1] W. sebi is one of three Wallemia species. 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 can reach 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.

References

[1] J Chemother. 2000 Feb;12(1):30-9. <http://www.ncbi.nlm.nih.gov/pubmed/10768513>

[2] R.J. Martinez. J Bacteriol. 2012 Apr;194(8):2113-4. <http://www.ncbi.nlm.nih.gov/genome/?term=Rahnella%20aquatilis>

[3] Robert Martinez, University of Alabama. <http://genome.jgi-psf.org/rahac/rahac.info.html>

[4] Park, Doo-Sang, Hyun-Woo Oh, Won-Jin Jeong, et al. "A Culture-Based Study of the Bacterial Communities within the Guts of Nine Longicorn Beetle Species and their Exo-enzyme Producing Properties for Degrading Xylan and Pectin." The Journal of Microbiology, October 2007, p. 394-401.

[5] Brenner, Don J., Hans E. Muller, Arnold G. Steigerwalt, et al. "Two new Rahnella genomospecies that cannot be phenotypically differentiated from Rahnella aquatilis." lnternstional Journal of Systematic Bacteriology (1 998), 48, 141 -149.

[6] Kim, Kil Yong, Diann Jordan, and Hari B. Krishnan. "Rahnella aquatilis, a bacterium isolated from soybean rhizosphere, can solubilize hydroxyapatite." FEMS Microbiology Letters Volume 153, Issue 2, 15 August 1997, Pages 273–277.

[7] Pintado, Manuela E., Ana I.E. Pintado, and F. Xavier Malcata. "Fate of Nitrogen During Metabolism of Whey Lactose by Rahnella aquatilis." Journal of Dairy Science, Volume 82, Issue 11, November 1999, Pages 2315-2326.

[8] Matsukura H., Katayama K., Kitano N., et al. "Infective endocarditis caused by an unusual gram-negative rod, Rahnella aquatilis." Pediatric Cardiology, 1996 Mar-Apr; 17(2): 108-11.

[9] Tash, Kaley. "Rahnella aquatilis Bacteremia from a Suspected Urinary Source." Journal of Clinical Microbiology. May 2005, vol. 43 no. 5, 2526-2528.

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