Discovery of leaderless bacteriocins through genome mining

Abstract

The emergence of antimicrobial resistance has prompted the search for antibiotic alternatives, and bacteriocins have emerged as promising alternatives to traditional antibiotics. Bacteriocins refer to a large family of antimicrobial peptides that are ribosomally synthesized by bacteria. The class of bacteriocins called leaderless bacteriocins is a unique group distinguished by the absence of a leader peptide and post-translational modifications, and hence their linear structures. Members of this class have been discovered by a traditional approach of screening bacterial isolates for antimicrobial activity and subsequently identifying the active molecule. This study presents the first extensive genome mining approach for leaderless bacteriocin discovery. In detail, we performed a precursor peptide-based genome mining to search for novel leaderless bacteriocins. Over 400 producer organisms with putative leaderless bacteriocins encoded in their genomes were identified, revealing the widespread occurrence of leaderless bacteriocins. Among the identified putative bacteriocins, 122 are unique peptide sequences. To validate our genome mining results, a novel bacteriocin we termed miticin, encoded in the genome of Streptococcus mitis, was obtained through chemical synthesis. Miticin was indeed found to be active, specifically against a wide range of Gram-positive bacteria. With this study, we provide the foundation for exploring a repertoire of potential novel antimicrobials identified through an innovative bioinformatics-guided approach, representing a significant leap compared to traditional screening and isolation methods for the discovery of bioactive molecules, specifically leaderless bacteriocins.