🔁⬇️ In S. epidermidis, we don’t observe an adolescent-specific increase in colonizations, but rather than lineage turnover is faster than C. acnes overall and decelerates by adulthood.

🧐 So when does microbiome engraftment happen?

📈🦠 We find that C. acnes colonization surges in adolescence during population expansion, apparently alleviating barriers to colonization before leveling off in adulthood. This period seems crucial for shaping the skin microbiome long-term.

🧑↔️🧔 Interestingly, in person-to-person spread, we see multiple transmitted genotypes of the same lineage coexist. This is a stark contrast to transmission in gut microbiomes where lineages originate from single founder cells, but supports previous work showing that skin pores allow coexistence.

☮️😌 We actually don’t find evidence of within-species metabolic niche partitioning (or adaptive selection) for either species, emphasizing the presence of neutrality and priority effects in the assembly of complex within-species communities.

👶1️⃣👦2️⃣🧓2️⃣ We found that there are essentially two types of face skin microbiomes or “Facial Cutotypes”: the younger, more diverse type (FC1) and the less diverse, C. acnes dominated adult-type (FC2).

🧫🌳 Using 4,055 isolate genomes from 8 families, we identified extremely closely related lineages of C. acnes & S. epidermidis. Since lineages arose from recent ancestors on people (<100 SNPs/genome in the entire lineage) we could use them to directly trace transmissions with high precision.