Our Social Circles Share Our Microbes

Scientists have long known our bodies host trillions of microbes, a complex inner jungle called the microbiome crucial for health. But how much of this microscopic world is truly ours, and how much is shared with those around us? Researchers asked this very question.

Investigating Microbial Transmission

To find answers, scientists gathered a massive collection of 9,715 human samples, including stool and saliva, from diverse groups across the globe. This included families, twins, and entire communities.

They used advanced genetic tools, like StrainPhlAn4, to zoom in on individual microbial strains—specific types of microbes within a species—rather than just broad categories. This allowed them to track the exact journey of these tiny passengers.

Key Findings on Sharing

The results show extensive microbial sharing, much like a handshake that exchanges not just warmth, but also microscopic life.

• Mothers and Infants: Showed the highest sharing, with a median of 50 percent of strains moving between them during the infant's first year.
• Cohabiting Households (Gut): Gut strain sharing dropped to 12 percent.
• Cohabiting Individuals (Oral): Oral microbes were even more social, with 32 percent shared.

The study found that “time since cohabitation affected strain sharing more than age or genetics.”

This person-to-person transmission is a major force in shaping our unique microbial signature. It suggests our social connections literally influence our internal biology.

As the authors state:

"The study’s key findings emphasize the extensive person-to-person transmission of the microbiome and its significance in shaping the individual microbiome's genetic makeup."

This is like realizing our personal garden isn't just seeded by what we plant, but also by seeds blowing in from our neighbors' gardens.