Diversity and taxonomy of Chaetomium and chaetomium-like fungi from indoor environments

During a study of indoor fungi, 145 isolates belonging toChaetomiaceaewere cultured from air, swab and dust samples from 19 countries. Based on the phylogenetic analyses of DNA-directed RNA polymerase II second largest subunit (rpb2), β-tubulin (tub2), ITS and 28S large subunit (LSU) nrDNA sequences, together with morphological comparisons with related genera and species, 30 indoor taxa are recognised, of which 22 represent known species, seven are described as new, and one remains to be identified to species level. In our collection, 69 % of the indoor isolates with six species cluster with members of theChaetomium globosumspecies complex, representingChaetomium sensu stricto. The other indoor species fall into nine lineages that are separated from each other with several known chaetomiaceous genera occurring among them. No generic names are available for five of those lineages, and the following new genera are introduced here:Amesiawith three indoor species,Arcopiluswith one indoor species,Collariellawith four indoor species,Dichotomopiluswith seven indoor species andOvatosporawith two indoor species. The generic concept ofBotryotrichumis expanded to includeEmilmuelleriaand the chaetomium-like speciesB. muromum(=Ch. murorum) in which two indoor species are included. The generic concept ofSubramaniulais expanded to include several chaetomium-like taxa as well as one indoor species.Humicolais recognised as a distinct genus including two indoor taxa. According to this study,Ch. globosumis the most abundantChaetomiaceaeindoor species (74/145), followed byCh. cochliodes(17/145),Ch. elatum(6/145) andB. piluliferum(5/145). The morphological diversity of indoorChaetomiaceaeas well as the morphological characteristics of the new genera are described and illustrated. This taxonomic study redefines the generic concept ofChaetomiumand provides new insight into the phylogenetic relationships among different genera withinChaetomiaceae.