A recent study published in Cell Host and Microbe provides a detailed look at how skin bacteria are shared—and not shared—among family members, challenging long-held assumptions about the dynamics of microbial transmission and stability. By combining metagenomic sequencing with bacterial isolate data, researchers focused on two prominent skin commensals: Cutibacterium acnes (C. acnes) and Staphylococcus epidermidis (S. epidermidis). Despite close physical proximity and shared environments, family members did not completely share bacterial lineages, revealing unexpected individuality in skin microbiome communities.
The researchers found that only 47% of C. acnes and 44% of S. epidermidis lineages were shared among two or more family members. In stark contrast, sharing between unrelated individuals—even those from the same school—was almost nonexistent. This suggests that while physical proximity facilitates some microbial transmission, stable engraftment of bacterial strains is still limited and highly individual. Between-family sharing, when observed, was rare and occurred at very low bacterial abundance, raising the possibility that these instances may reflect experimental noise rather than true biological transmission.
Even within families, the data reveal that most parents harbored distinct microbial lineages. For instance, 23 of 37 C. acnes and 23 of 28 S. epidermidis lineages on parents were not shared with their spouse, indicating that adult skin environments resist colonization by foreign strains—even from partners. This individuality likely reflects biological barriers to colonization, such as priority effects, where early colonizers outcompete newcomers, or selective pressures unique to each person’s skin environment.
Daniel Lieberman, senior author of the study, highlighted this connection: “We found that there are some surprising dynamics, and these dynamics provide insights for how to design probiotic therapy. f we had a strain that we knew could prevent acne, these results would suggest we should make sure we apply them early during the transition to adulthood, to really get them to engraft.” The suggestion here is that early life, particularly adolescence, represents a window of opportunity during which beneficial microbes may be more likely to successfully colonize the skin.
This study emphasizes the importance of considering both microbial stability and individuality when designing interventions for skin health. It reveals a nuanced view of microbial transmission—not governed solely by contact or environment, but also by biological selectivity, timing, and community context.
Sources: Cell Host and Microbe, EurekAlert