Wallemia sebi is a cosmopolitan, xerophilic mold-like fungus that is often isolated from foods with high sugar or salt content as well as from aerial dust. Wallemia sebi has been implicated as the causal agent in some human subcutaneous infections and respiratory disease. Several characteristics place Wallemia species, of which there are three, apart from other known fungi: they possess a unique form of conidiogenesis, are among the most xerotolerant fungi known, and hold an isolated phylogenetic position within the Basidiomycota as the sister class to all other Agaricomycotina (mushroom-forming fungi). Almost nothing is known about its ecology or biology. Researchers have sequenced the genome of W. sebiin order to understand its adaptations for surviving in osmotically challenging environments. Genomic data were also used to finally resolve the relationship of Wallemia which has helped to re-evaluate hypotheses about the evolution of basidiomycetes. Wallemia sebi has a compact genome (9.8 Mb), with few repeats and the largest fraction of genes with functional domains compared with other Basidiomycota. Despite the seemingly reduced genome, several gene family expansions and a high number of transporters were found that provide clues to the ability of W. sebi to colonize harsh environments.
Matheny, PB, et al. (2006) Resolving the phylogenetic position of the Wallemiomycetes: an enigmatic major lineage of Basidiomycota. Can J Bot 84, 1794-1805.