Antimicrobial and antibiofilm effects of a leucine-substituted rice peptide against Porphyromonas gingivalis and Fusobacterium nucleatum

The aim of this study to elucidate the antibacterial and antibiofilm effects of a leucine-substituted peptide against periodontal pathogen. N3L peptide was designed as a leucine-substituted variant of the rice-derived AmyI-1-18 peptide. Subsequently, the minimum inhibitory concentration and minimum bactericidal concentration of N3L against Porphyromonas gingivalis and Fusobacterium nucleatum were determined. Furthermore, its membrane permeability was investigated by propidium iodide (PI) staining. Moreover, the effects of N3L on the gene expression of virulence factors were analyzed by reverse transcriptase quantitative polymerase chain reaction. The biofilm amount was assessed by crystal violet staining to analyze the biofilm control ability of N3L peptide. N3L demonstrated bactericidal activity against P. gingivalis and F. nucleatum, with notably enhanced antimicrobial activity against P. gingivalis compared with the parent peptide AmyI-1-18. PI staining indicated that N3L showed bacterial membrane permeability against P. gingivalis and F. nucleatum. Moreover, N3L significantly downregulated the expression levels of fimA, rgpA, rgpB, and kgp in P. gingivalis and fadA in F. nucleatum. This peptide also significantly inhibited biofilm formation and reduced established biofilms of P. gingivalis and F. nucleatum. The leucine-substituted rice peptide N3L, with its hydrophobicity and α-helix content higher than those of AmyI-1-18, showed enhanced antimicrobial and antibiofilm activities through membrane disruption and modulation of gene expressions related to adherence and metabolism. The leucine-substituted rice peptide N3L showed enhanced antimicrobial and antibiofilm activities against P. gingivalis and F. nucleatum.