A close examination of human skin found that each pore had a single variety of bacteria living inside.

A study co-authored by MIT researchers—including Tami Lieberman, a core member of the IMES Faculty— finds each pore on the human face holds a different variety of Cutibacterium acnes bacteria. “Each person’s skin had a unique combination of strains, but what surprised the researchers most was that each pore housed a single variety of C. acnes.” A paper about the research was recently accepted in Cell Host & Microbe. The summary is here:

What enables strains of the same species to coexist in a microbiome? Here, we investigate whether host anatomy can explain strain co-residence of Cutibacterium acnes, the most abundant species on human skin. We reconstruct on-person evolution and migration using whole-genome sequencing of C. acnes colonies acquired from healthy subjects, including from individual skin pores, and find considerable spatial structure at the level of pores. Although lineages (sets of colonies separated by <100 mutations) with in vitro fitness differences coexist within centimeter-scale regions, each pore is dominated by a single lineage. Moreover, colonies from a pore typically have identical genomes. An absence of adaptive signatures suggests a genotype-independent source of low within-pore diversity. We therefore propose that pore anatomy imposes random single-cell bottlenecks; the resulting population fragmentation reduces competition and promotes coexistence. Our findings suggest that therapeutic interventions involving pore-dwelling species might focus on removing resident populations over optimizing probiotic fitness.

Read the full story about the new research via The New York Times.