The study reveals that many well-known gut bacteria actually split into several distinct evolutionary lineages, each adapted to different gut environments, challenging the traditional species-level view of the microbiome.

These within-species populations are linked to health conditions such as diabetes, cancer, and aging, underscoring their potential role in disease and aging processes.

The findings point toward a precision-medicine future for microbiome health, where therapies target harmful bacterial populations without disrupting beneficial ones.

In practical terms, microbiome medicine could become more precise by focusing on specific bacterial populations rather than entire species, aiding biomarker discovery and targeted therapies that promote beneficial strains while suppressing harmful ones.

Researchers aim to identify the genes and functional differences that separate these populations to better understand their roles in biology and disease.

The work analyzes thousands of gut bacterial isolates and extensive metagenomic data from diverse countries, ages, and health conditions, using bioinformatics to infer adaptation and specialization in the gut.

Within-species populations are associated with health states such as aging, inflammatory bowel disease, colorectal cancer, and type 2 diabetes, suggesting sharper microbiome biomarkers when focusing on populations rather than species.

A key observation is genome-wide selective sweeps that reduce diversity within successful populations, producing highly similar yet functionally distinct lineages that differ from neighboring populations.

The study notes that competitive bacterial populations can spread rapidly across continents, illustrating the dynamic and global nature of gut bacteria.

Some gut bacteria can travel between people worldwide over decades, influencing how microbiomes are maintained and transferred across populations.

Using reverse ecology and global data, the University of Vienna study shows that what were thought to be single gut species are actually multiple distinct groups adapted to different body sites.

Researchers employed reverse ecology to reveal that many bacterial species harbor several evolutionarily distinct populations tuned to different gut environments.