Skin microbiome: looking back to move forward

Abstract

Trillions of bacteria, fungi, viruses, archaea, and small arthropods colonize the skin surface, collectively comprising the skin microbiome. Generations of researchers have classified these microbes as transient versus resident, beneficial versus pathogenic, and collaborators versus adversaries. Culturing and direct sequencing of microbial inhabitants identified distinct populations present at skin surface sites. Herein, we explore the history of this field, describe findings from the current molecular sequencing era, and consider the future of investigating how microbes and antimicrobial therapy contribute to human health.

Figure 1. Schematic of skin histology viewed in cross-section with microorganisms and skin appendages

Microorganisms (virus, bacteria and fungi, mites) cover the surface of the skin and reside deep within the hair and glands.

Figure 2. Homonculus showing major sites and range of Propionibacterium acnes colonization

Classic microbiologists swabbed and cultured diverse sites to characterize the predominant sites of colonization (“headquarters”) and general distribution (“range”). Adapted from Marples’ “The Ecology of the Human Skin”.

Figure 3. Topographical distribution of bacteria on skin sites

The skin microbiome is highly dependent on the microenvironment of the sampled site. Sebaceous sites are labeled in blue, moist sites are labeled in green and dry surfaces are labeled in red. Family-level classification of bacteria colonizing an individual subject is shown. Data is from Grice et al, 2009.

Figure 4. Interpersonal variation of the skin microbiome

Characterization of the skin microbiota, as determined by 16S rRNA sequencing, of four sites on four healthy volunteers (HV1, HV2, HV3, HV4) is depicted. Skin microbial variation is more similar dependent on the site than the individual. A. Antecubital crease; B. Back; C. Nare; D. Plantar heel. Data from Grice et al, 2009.