Abstract
BackgroundPropionibacteria are part of the human microbiota. Many studies have addressed the predominant colonizer of sebaceous follicles of the skin, Propionibacterium acnes, and investigated its association with the skin disorder acne vulgaris, and lately with prostate cancer. Much less is known about two other propionibacterial species frequently found on human tissue sites, Propionibacterium granulosum and Propionibacterium avidum. Here we analyzed two and three genomes of P. granulosum and P. avidum, respectively, and compared them to two genomes of P. acnes; we further highlight differences among the three cutaneous species with proteomic and microscopy approaches.ResultsElectron and atomic force microscopy revealed an exopolysaccharide (EPS)-like structure surrounding P. avidum cells, that is absent in P. acnes and P. granulosum. In contrast, P. granulosum possesses pili-like appendices, which was confirmed by surface proteome analysis. The corresponding genes were identified; they are clustered with genes encoding sortases. Both, P. granulosum and P. avidum lack surface or secreted proteins for predicted host-interacting factors of P. acnes, including several CAMP factors, sialidases, dermatan-sulphate adhesins, hyaluronidase and a SH3 domain-containing lipoprotein; accordingly, only P. acnes exhibits neuraminidase and hyaluronidase activities. These functions are encoded on previously unrecognized island-like regions in the genome of P. acnes.ConclusionsDespite their omnipresence on human skin little is known about the role of cutaneous propionibacteria. All three species are associated with a variety of diseases, including postoperative and device-related abscesses and infections. We showed that the three organisms have evolved distinct features to interact with their human host. Whereas P. avidum and P. granulosum produce an EPS-like surface structure and pili-like appendices, respectively, P. acnes possesses a number of unique surface-exposed proteins with host-interacting properties. The different surface properties of the three cutaneous propionibacteria are likely to determine their colonizing ability and pathogenic potential on the skin and at non-skin sites.
Highlights
Propionibacteria are part of the human microbiota
Despite their omnipresence on human skin little is known about the role of cutaneous propionibacteria
Four genomes were available from public databases (P. acnes KPA171202 (KPA) (GenBank: AE017283) [16], P. acnes 266 (GenBank: CP002409) [21], P. avidum 44067 (CP005287) [22] and P. avidum ATCC25577 (GenBank: NZ_AGBA00000000)) and we draft sequenced three additional ones (P. granulosum DSM20700 and TM11) and P. avidum TM16
Summary
Propionibacteria are part of the human microbiota. Many studies have addressed the predominant colonizer of sebaceous follicles of the skin, Propionibacterium acnes, and investigated its association with the skin disorder acne vulgaris, and lately with prostate cancer. Much less is known about two other propionibacterial species frequently found on human tissue sites, Propionibacterium granulosum and Propionibacterium avidum. The genus Propionibacterium belongs to the phylum Actinobacteria and contains classical (or dairy) and cutaneous species. Whereas classical species such as Propionibacterium freudenreichii are considered to have probiotic effects [1] and are rather well characterized due to their importance in the dairy industry, cutaneous species are less well understood. The three most important cutaneous species are P. acnes, P. avidum and P. The role of human-associated bacterial species belonging to the genus Propionibacterium is largely unknown; these species are described as commensals, saprophytes, parasites or opportunistic pathogens. Little is known about the association of P. avidum and P. granulosum with human diseases. The disease association of P. granulosum is less clear, though it has been found in a few cases of endocarditis and endophthalmitis, and has been associated, like P. acnes, with sarcoidosis [14,15]
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