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Scientific classification
Kingdom: Fungi
Division: Basidiomycota
Class: Wallemiomycetes
Zalar, de Hoog & Schroers (2005)[1]
Order: Wallemiales
Zalar, de Hoog & Schroers (2005)
Family: Wallemiaceae
R.T. Moore (1966)[2]
Genus: Wallemia
Johan-Olsen (1887)
Type species
Wallemia ichthyophaga

W. ichthyophaga
W. muriae
W. sebi

The Wallemiomycetes are a class of fungi in the division Basidiomycota. It consists of the single order Wallemiales, containing the single family Wallemiaceae, which in turn contains the single genus Wallemia. The phylogenetic origin of the lineage was placed to various parts of Basidiomycota, but according to the analysis of a larger dataset it is a sister group of Agaricomycotina.[3][4] The genus contains species of xerophilic molds that are found worldwide. The three described species (W. sebi, W. muriae, and W. ichthyophaga) are distinguished by size range of conidia (asexual spores), the degree of xerotolerance and ribosomal DNA sequences.[1] They are typically isolated from low-moisture foods (such as cakes, bread, sugar, peanuts, dried fish), indoor air dust, salterns and soil.[1] W. sebi is thought to be one of the causes of the hypersensitivity pneumonitis known as the farmer's lung disease,[5] but since the other two species were recognised and separated from W. sebi only recently, their role in the disease cannot be excluded.[1]

Tolerance to low water activity is generally much more frequent among ascomycetous than basidomycetous fungi, and xerotolerant fungi are also able to grow in regular growth media with normal water activity (unlike, for example, halophilic Archaea).[6] However, species from the genus Wallemia are an exception to both of these rules: all three species can tolerate high concentrations of sugars and salts (W. ichthyophaga grows even in media saturated with sodium chloride), while W. muriae and W. ichthyophaga cannot be cultivated unless the water activity of the medium is lowered.[1]

Cell wall and morphological changes of Wallemia species are thought to play a major role in adaptation to low water activity.[7]

The whole genome sequences of W. sebi[3] and W. ichthyophaga[4] are available.


  1. ^ a b c d e Zalar P, de Hoog GS, Schroers HJ, Frank JM, Gunde-Cimerman N. (2005). "Taxonomy and phylogeny of the xerophilic genus Wallemia (Wallemiomycetes and Wallemiales, cl. et ord. nov.)". Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology 87 (4): 311–28. doi:10.1007/s10482-004-6783-x. PMID 15928984. 
  2. ^ Sneh B, Jabaji-Hare S, Neate S, Dijst G. (1996). Rhizoctonia species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. Springer. p. 20. ISBN 978-0-7923-3644-0. 
  3. ^ a b Padamsee, M.; Kumar, T. K. A.; Riley, R.; Binder, M.; Boyd, A.; Calvo, A. M.; Furukawa, K.; Hesse, C.; Hohmann, S.; James, T. Y.; Labutti, K.; Lapidus, A.; Lindquist, E.; Lucas, S.; Miller, K.; Shantappa, S.; Grigoriev, I. V.; Hibbett, D. S.; McLaughlin, D. J.; Spatafora, J. W.; Aime, M. C. (2012). "The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction". Fungal Genetics and Biology 49 (3): 217–226. doi:10.1016/j.fgb.2012.01.007. PMID 22326418. 
  4. ^ a b Zajc, J.; Liu, Y.; Dai, W.; Yang, Z.; Hu, J.; Gostin Ar, C.; Gunde-Cimerman, N. (2013). "Genome and transcriptome sequencing of the halophilic fungus Wallemia ichthyophaga: Haloadaptations present and absent". BMC Genomics 14: 617. doi:10.1186/1471-2164-14-617. PMID 24034603.  edit
  5. ^ Reboux, G.; Piarroux, R.; Mauny, F. D. R.; Madroszyk, A.; Millon, L.; Bardonnet, K.; Dalphin, J. C. (2001). "Role of Molds in Farmer's Lung Disease in Eastern France". American Journal of Respiratory and Critical Care Medicine 163 (7): 1534–1539. doi:10.1164/ajrccm.163.7.2006077. PMID 11401869.  edit
  6. ^ GostinäAr, C.; Grube, M.; De Hoog, S.; Zalar, P.; Gunde-Cimerman, N. (2010). "Extremotolerance in fungi: Evolution on the edge". FEMS Microbiology Ecology 71 (1): 2–11. doi:10.1111/j.1574-6941.2009.00794.x. PMID 19878320. 
  7. ^ Kralj Kuncic, M.; Kogej, T.; Drobne, D.; Gunde-Cimerman, N. (2009). "Morphological Response of the Halophilic Fungal Genus Wallemia to High Salinity". Applied and Environmental Microbiology 76 (1): 329–337. doi:10.1128/AEM.02318-09. PMC 2798636. PMID 19897760.