Peptide LQLY3-1, a novel Vibrio harveyi quorum sensing inhibitor produced by Lactococcus lactis LY3-1

Vibrio harveyi is one of the main pathogenic bacteria in the aquaculture industry, and quorum sensing (QS) plays key role in its pathogenicity. Previous studies have demonstrated that a metabolite with protein properties isolated from Lactococcus lactis LY3-1 showed anti-QS activity against V. harveyi. In this study, this metabolite of L. lactis LY3-1 was identified as peptide LQLY3-1, with a 1.09 kDa molecular mass, which was purified via ethyl acetate extraction followed by ultrafiltration, Sephadex G25 gel chromatography, and high-performance liquid chromatography. Its amino acid sequence was ALSLVKIHGR, as demonstrated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Crude extracts of peptide LQLY3-1 at sub-minimum inhibitory concentrations inhibited V. harveyi biofilm formation and the production of virulence factors, including exopolysaccharide, proteolytic enzymes, hemolysin, gelatinase, and motility, albeit without inhibiting bacterial growth. Scanning electron microscopy images indicated that the crude extracts of peptide LQLY3-1 disrupted the integrity of the V. harveyi biofilm. Additionally, molecular docking analysis indicated that peptide LQLY3-1 could competitively bind to the LuxN receptor protein with its natural ligand N-octanoyl-l-homoserine lactone, thereby blocking the signal transmission of the QS system. These results suggested that peptide LQLY3-1 can be used as a promising QS inhibitor to control V. harveyi pathogenicity.