Genome of C. kroppenstedtii subsp. demodicis. Genome of C. kroppenstedtii subsp. demodicis

Background: Demodex mites flourish in their niche habitat, the pilosebaceous unit, although they are frequently exposed to harsh conditions – like intense heat, UV-A/B radiation, varying salinity or different cosmetics. Their recently characterized endobacterium might aid their survival under those hostile conditions. Objectives: The aim of this study was to elucidate mechanisms of the microbe-host-interaction alleviating the environmental stress Demodex mites are exposed to. Methods: The genome of the endobacterium Corynebacterium kroppenstedtii subsp. demodicis was sequenced using PacBio third generation sequencing. Using the MicroScope system, the genome was automatically annotated (calculation of orthologs was based on bidirectional best BLASTP hits) and partially manually curated. KEGG metabolic pathways was used to analyze the primary and secondary metabolism and in combination with the secretome of Demodex folliculorum (via the previously described transcriptome using SignalP) their symbiotic interaction in the mites' digestion. Results: Sequencing yielded a single contig with a size of 2,456,075bp and resulted in the prediction of 2030 coding sequences. Comparative genomics revealed a core genome of 743 genes and a reduced set of variable genes benchmarked against other members of the genus. Pathway analysis of the primary metabolism showed an almost complete "minimal gene set" lacking two tRNA synthetases and genes for the biosynthesis of phosphatidylethanolamine and NAD+. Compared to other corynebacteria, many carbohydrate biosynthesis pathways are incomplete and fatty acid synthase I is missing. Secondary metabolic traits include a complete mevalonate and β-carotene biosynthesis pathway, but no methylerythritol phosphate pathway. Additionally, to UV protection via β-carotene, cytoprotective ClpB, DNA (RecN) and protein (MsrA) repair enzymes as well as catalase (KatA), superoxide dismutase (SodA) and a ROS-quenching manganese ABC transporter (SitB) were found. The secretome yielded different hydrolases (lipase, phosphatase, glucosidase, peptidase) putatively aiding in digestion. Conclusions: The present study reveals in-depth details on the microbe-host-interaction.