Bacteriocin-mediated intraspecies competition driven by acquired Bac41 operon in epidemic Enterococcus faecalis ST179

Enterococcus faecalis is a common gut commensal and an opportunistic pathogen causing hospital-acquired infections. Despite its clinical importance, comprehensive global genomic and epidemiological data remain limited. Here, we analyzed 5,895 E. faecalis genomes collected between 2000 and 2020 and identified ST179, a human-derived single-operon variant of the high-risk CC16 clonal complex, as an emerging epidemic clone in China. Spot-killing assays revealed that ST179 strongly inhibited other clinical E. faecalis sequence types. Biochemical purification and proteomic analyses identified BacL1 as a key effector associated with this species-specific antibacterial activity. Functional assays confirmed its inhibitory phenotype, providing ST179 with a lineage-specific, bacteriocin-mediated competitive advantage. The high prevalence of the Bac41 operon likely contributed to the epidemiological success and ecological fitness of ST179. These findings highlight the role of bacteriocin-mediated intraspecies competition in shaping E. faecalis population dynamics and suggest that ST179 might become an emerging high-risk lineage in China.IMPORTANCEEnterococcus faecalis is a common gut bacterium and an opportunistic pathogen. We identify ST179 as an emerging epidemic clone in China and show that it outcompetes other strains via the bacteriocin Bac41. This competitive advantage helps explain its rapid spread. Our findings highlight how bacterial competition shapes population dynamics and provide insights into the emergence of high-risk E. faecalis lineages, informing strategies for monitoring and infection control.