L-lysine as a Potential Agent for Controlling Biofilm Formation Using Fusobacterium nucleatum and Porphyromonas gingivalis

Periodontitis, a globally-pervasive chronic inflammatory condition, is precipitated by forming microbial biofilms. A key player in this process is Fusobacterium nucleatum (F. nucleatum), an anaerobic bacterium exhibiting invasive and pro-inflammatory characteristics primarily associated with the onset of periodontitis. Consequently, developing novel biofilm control strategies specifically targeting F. nucleatum is essential.

The objective of this research is to examine the suppressive impact of L-lysine on biofilm formation using F. nucleatum.

Fusobacterium nucleatum(F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) were cultured in a liquid medium containing L-lysine of different concentrations. The antimicrobial activity of L-lysine was evaluated using the broth microdilution method. The effect of L-lysine on the mono-species and dual-species F. nucleatum biofilms was assessed using techniques such as crystal violet staining. The synthesis of extracellular polysaccharide substances (EPSs) from biofilms was measured using phenol-sulfuric acid. The expression level of virulence factors (FN1420, FN0669, FN0634, FN1162) and the biofilm-formation-related gene radD were quantified using real-time PCR.

L-lysine exhibited the antibacterial and antibiofilm activity of F. nucleatum and F. nucleatum/ P. gingivalis double strains, which was concentration-dependent. The MIC and MBC values were 10 mg/ml and 20 mg/ml in F. nucleatum single strains, while those in F. nucleatum/ P. gingivalis double strains were 20 mg/ml and 40 mg/ml. L-lysine with a concentration ≥20 mg/ml could reduce the EPS production in F. nucleatum and F. nucleatum/ P. gingivalis dual-species biofilms. L-lysine also inhibited the expression of genes encoding the F. nucleatum virulence factor (FN1420, FN0669, FN0634, FN1162) and the adhesive factor radD.

These findings corroborate the potential of L-lysine as an agent impeding the development of both mono-species biofilms of F. nucleatum and dual-species biofilms of F. nucleatum and P. gingivalis.