Strains to go: interactions of the skin microbiome beyond its species

An extraordinary biodiversity of bacteria, fungi, viruses, and even small multicellular eukaryota inhabit the human skin. Genomic innovations have accelerated characterization of this biodiversity both at a species as well as the subspecies, or strain level, which further imparts a tremendous genetic diversity to an individual's skin microbiome. In turn, these advances portend significant species- and strain-specificity in the skin microbiome's functional impact on cutaneous immunity, barrier integrity, aging, and other skin physiologic processes. Future advances in defining strain diversity, spatial distribution, and metabolic diversity for major skin species will be foundational for understanding the microbiome's essentiality to the skin ecosystem and for designing topical therapeutics that leverage or target the skin microbiome.