970 Taxonomical clarification and overview of six cutibacterium species including recently described species cutibacterium modestum and cutibacterium porci by genomic and proteomic methods

Background: Recent descriptions of two new species of genus Cutibacterium resulted in a further expansion of the taxonomical tree of the genus, which include Cutibacterium acnes. One of the new species, Cutibacterium modestum, was coined in 2020 by the presenter as the fifth species of genus Cutibacterium, which had been tentatively named as “Propionibacterium humerusii”. Another new species, Cutibacterium porci, was firstly isolated from porcine faeces by Wylensek et al. in 2020, being the first Cutibacterium species possibly the only non-human member of the genus. Following these new findings, researchers need a map of status quo of the genus. Methods: To describe the comprehensive view of the species and subspecies of the genus and to verify their taxonomical positions, we applied three of the several taxonomical tools, which are in silico DNA-DNA hybridization, the average nucleotide identity, and MALDI-TOF mass spectrometry. Results: Our genome-based approaches (in silico DNA-DNA hybridization and the average nucleotide identity) enabled the tree view of these species and subspecies, and verified the individual status of the species/subspecies by the pairwise similarity values (species cutoff: 70% in in silico DNA-DNA hybridization and 95% in the average nucleotide identity; subspecies cutoff: 79% and 99%, respectively). Furthermore, the proteomic approach (MALDI-TOF mass spectrometry) showed the effective differentiation of these species/subspecies by using 3,000-15,000 m/z range of the spectral patterns of this latest identifying tool. Discussion: Dermatological researchers are to see these new species names in coming years. Our presenting information will help them to understand the taxonomical background and get more familiarized to these names.