A Taxonomic Revision of the Wallemia sebi Species Complex

Wallemia sebi is a xerophilic food- and air-borne fungus. The name has been used for strains that prevail in cold, temperate and tropical climates. In this study, multi-locus phylogenetic analyses, using the internal transcribed spacer (ITS) regions, DNA replication licensing factor ( MCM7 ), pre-rRNA processing protein ( TSR1 ), RNA polymerase II largest subunit ( RPB1 ), RNA polymerase II second largest subunit ( RPB2 ) and a new marker 3´-phosphoadenosine-5´-phosphatase ( HAL2 ), confirmed the previous hypothesis that W . sebi presents a complex of at least four species. Here, we confirm and apply the phylogenetic analyses based species hypotheses from a companion study to guide phenotypic assessment of W . sebi like strains from a wide range of substrates, climates and continents allowed the recognition of W . sebi sensu stricto and three new species described as W . mellicola , W . Canadensis , and W . tropicalis . The species differ in their conidial size, xerotolerance, halotolerance, chaotolerance, growth temperature regimes, extracellular enzyme activity profiles, and secondary metabolite patterns. A key to all currently accepted Wallemia species is provided that allow their identification on the basis of physiological, micromorphological and culture characters.