Microbial strain-level population structure and genetic diversity from metagenomes

Area of Science:

• Microbiology
• Genetics
• Bioinformatics

Background:

• Human health conditions are often linked to specific microbial strains, not just entire groups.
• Characterizing individual microbial strains is crucial but challenging with current metagenomic techniques.

Purpose of the Study:

• To introduce StrainPhlAn, a novel approach for metagenomic strain identification.
• To analyze the genetic structure and population genetics of thousands of gut microbial strains across diverse human populations.

Main Methods:

• Developed StrainPhlAn for per-sample dominant sequence variant reconstruction within species-specific marker genes.
• Applied the method to over 1500 gut metagenomes from global populations (North/South American, European, Asian, African).

Main Results:

• Identified predominantly subject-specific strain variants with low inter-subject sharing (<5%).
• Found that a single dominant strain typically persists within a species over time (>70% of species).
• Correlated microbial population structure with host geographic origin, showing distinct subspecies or continuous genetic variations linked to geography.

Conclusions:

• StrainPhlAn provides a comprehensive, strain-level genetic overview of gut microbial diversity.
• Revealed geographic structuring of gut microbial populations and estimated genetic variability across species, with some species like *Bacteroides* being highly consistent and others like *P. copri* being more plastic.