Pangenomics of Limosilactobacillus fermentum reveals genomic diversity and bacteriocin activity against Staphylococcus aureus and Escherichia coli

Limosilactobacillus fermentum is a versatile lactic acid bacterium with significant probiotic and biotechnological potential, yet the genomic determinants underlying its ecological adaptation and therapeutic applications remain underexplored. This study performed a comparative genomic analysis of 52 L. fermentum strains, with a focus on the novel strain ATT-06 isolated from traditional Turkish shalgam. We uncovered substantial genetic diversity, evidenced by an open pan-genome (18,647 genes) and a small core genome (718 genes). CRISPR-Cas systems were prevalent (46 strains), with Type-IE and Type-IIA being most common and mutually exclusive from Type-IC. Strain ATT-06, which uniquely produced gamma-aminobutyric acid at 17.74 µg/mL, harbored a Type-IIA CRISPR system and a single prophage. In silico molecular docking and dynamics simulations revealed that the bacteriocin Lactococcin, encoded by strain ATA-LTC-Lf170503, exhibited strong binding affinities (ΔG: -8.1 to -13.0 kcal/mol) against Rho proteins of Staphylococcus aureus and Escherichia coli, outperforming Acidocin A. These findings highlight the genomic plasticity and adaptive mechanisms of L. fermentum, and position strain ATT-06 as a promising probiotic candidate with potential neuroactive and antimicrobial applications.