Revealing the diversity of commensal corynebacteria from a single human skin site

Background Our understanding of the skin microbiome has dramatically improved since the pioneering studies and the improvements in sequencing technologies. Species of the genus Corynebacterium are known to form a major part of the human skin microbiome but most detailed studies have focussed on other similarly prevalent genera like Staphylococcus and Cutibacteria. Prior to this study, there were few complete genomes for skin commensals of the genus Corynebacterium, with only 9 complete genomes available for the most commonly identified species C. tuberculostearicum.

Results In this study we explored the genus Corynebacterium from a single body site by swabbing the axilla/underarm of 4 individuals and using a selective media to enrich for corynebacteria. We then generated whole genome sequencing data of these corynebacteria enriched isolates using long-read sequencing and subsequent bioinformatics analysis to reveal an unparalleled diversity of this genus from a single skin site. Through this approach, we obtained the closed genomes of 215 isolates, 154 derived from a single individual. With this genetic information, we were able to identify 7 different species including species previously not associated to the skin and two novel species provisionally named C. axilliensis and C. jamesii. We used pangenome analysis on 30 genetically distinct isolates spanning the 7 species to identify putative metabolic differences, antimicrobial resistance profiles, novel biosynthetic gene clusters (BGCs), prophages and phage defence systems.

Conclusions Our culture-based Nanopore sequencing approach has dramatically improved our overall knowledge of skin corynebacteria, and uniquely here also providing in-depth analysis from a single skin site, revealing a multitude of differences between the isolates. Here we not only improved our knowledge of axillary corynebacteria but also greatly expanded the publicly available number of cutaneous corynebacterial genomes complementing recent studies seeking to understand the diversity of skin corynebacteria.