Wallemia sebi
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
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
Rahnella aquatilis is a facultative anaerobe (it can live in the absence or presence of oxygen) that fixes Nitrogen [2]. R. aquatilis metabolizing whey lactose produces high levels of organic acids (except for lactic acid) [7].
Ecology
Rahnella aquatilis is named so because of its prevalence in fresh water. It has been found around the globe in places like the United States, Korea, Japan, Russia, the Ukraine, and Egypt. R. aquatilis has also been found in humans, soil, and snails [5]. One of the most unusual places for the the microbe to have been found was inside the gut of certain speicies of longicorn beetles in Korea [4].
Pathology
Rahnella aquatilis is pathogenic in humans. The organism can be diagnosed in patients via blood cultures, respiratory washings, and in wound cultures. Various infections, such as bacteremia (from renal infection), sepsis, respiratory infection, and urinary tract infection can be the result. One case involved an 11-month-old girl with congenital heart disease who developed infective endocarditis [8]. Another case involved a 76-year-old male who had prostatic hyperplasia presenting with acute pyelonephritis [9]. It is noted that R. aquatilis can potentially cause life-threatening infections in humans, infants and adults alike, especially the immunocompromised and organ transplant recipients. Treatments have included intravenous and oral levofloxacin therapy (and other members of the quinolone family).
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
