Uncovering the arsenal of class II bacteriocins in salivarius streptococci

Abstract

Facing the antibiotic resistance crisis, bacteriocins are considered as a promising alternative to treat bacterial infections. In the human commensal Streptococcus salivarius, the production of unmodified bacteriocins (or salivaricins) is directly controlled at the transcriptional level by quorum-sensing. To discover hidden bacteriocins, we harnessed here the unique molecular signatures of salivaricins not yet used in available computational pipelines and performed genome mining followed by orthogonal reconstitution and expression. From 100 genomes of S. salivarius, we identified more than 50 bacteriocin candidates clustered into 21 groups. Strain-based analysis of bacteriocin combinations revealed significant diversity, reflecting the plasticity of seven independent loci. Activity tests showed both narrow and broad-spectrum bacteriocins with overlapping activities against a wide panel of Gram-positive bacteria, including notorious multidrug-resistant pathogens. Overall, this work provides a search-to-test generic pipeline for bacteriocin discovery with high impact for bacterial ecology and broad applications in the food and biomedical fields.

Class II bacteriocins in the Streptococcus salivarius pan-genome were bioinformatically identified based on conserved sequence properties. These diverse “salivaricins” show antibacterial activity against Gram-positive pathogens.