The morphology of three phenetically identical Penicillium isolates, collected from the bioaerosol
in a restoration laboratory in Italy, displayed macro- and microscopic characteristics that were
similar though not completely ascribable to Penicillium raistrickii. For this reason, a phylogenetic
approach based on DNA sequencing analysis was performed to establish both the taxonomic
status and the evolutionary relationships of these three peculiar isolates in relation to previously
described species of the genus Penicillium. We used four nuclear loci (both rRNA and protein
coding genes) that have previously proved useful for the molecular investigation of taxa belonging
to the genus Penicillium at various evolutionary levels. The internal transcribed spacer region
(ITS1–5.8S–ITS2), domains D1 and D2 of the 28S rDNA, a region of the tubulin beta chain gene
(benA) and part of the calmodulin gene (cmd) were amplified by PCR and sequenced. Analysis of
the rRNA genes and of the benA and cmd sequence data indicates the presence of three
isogenic isolates belonging to a genetically distinct species of the genus Penicillium, here
described and named Penicillium simile sp. nov. (ATCC MYA-4591T 5CBS 129191T). This
novel species is phylogenetically different from P. raistrickii and other related species of the genus
Penicillium (e.g. Penicillium scabrosum), from which it can be distinguished on the basis of
morphological trait analysis.