Strain-level dynamics of Akkermansia muciniphila in the human gut microbiota.

Akkermansia muciniphila (Akk), a mucin-degrading bacterium residing in the human gut, plays a pivotal role in intestinal health. This study investigated its temporal dynamics, strain-level diversity, and cross-regional transmission using longitudinal metagenomic data from the Chinese Microbiome Project (CMP). We observed significant fluctuations in Akk relative abundance across 52 time points in 7 healthy individuals, with detection rates of 56.9% (16S rRNA gene sequencing) and 33.3% (whole-genome sequencing, WGS). Notably, "short-term blooms"--rapid increases followed by declines in relative abundance--were identified in multiple subjects. Genomic analysis of 39 Akkermansia metagenome-assembled genomes (MAGs), combined with 89 publicly available strains with complete genome, revealed phylogenetically distinct clusters (average nucleotide identity, ANI < 98% between clusters). Strikingly, individuals harbored different clusters at varying time points (e.g., AmII replaced by AmIb and later AmIa in subject P4), suggesting strain replacement and recurrent colonization. Furthermore, high-similarity strains (ANI > 99%) were shared between individuals with close contact (e.g., cohabiting subjects P2 and P4) and across geographically distant regions (China, South Korea, and the United States), implicating human-mediated or environmental transmission pathways. These findings underscore the dynamic nature of Akk within the gut microbiota and highlight the need to explore factors driving its colonization, strain competition, and ecological dissemination.