Arginine replacement of histidine on temporin-GHa enhances the antimicrobial and antibiofilm efficacy against Staphylococcus aureus.

Antimicrobial peptides (AMPs) show broad-spectrum microbicidal activity against bacteria, fungi, and viruses, and have been considered as one of the most promising candidates to overcome bacterial antimicrobial resistance. Structural modification of AMPs is an effective strategy to develop high-efficiency and low-toxicity antibacterial agents. A series of peptides GHaR6R, GHaR7R, GHaR8R, and GHaR9W with arginine replacement of histidine (His) derived from temporin-GHa of Hylarana guentheri were designed and synthesized. These derived peptides exhibit antibacterial activity against Staphylococcus aureus, and GHaR8R exerts bactericidal effect within 15 min at 4 × MIC (25 µm). The derived peptides caused rapid depolarization of bacteria, and the cell membrane damage was monitored using quartz crystal microbalance with dissipation assay, which suggests that they target cell membranes to exert antibacterial effects. The derived peptides can effectively eradicate mature biofilms of S. aureus. Taken together, the derived peptides are promising antibacterial agent candidates against S. aureus.

Four temporin-derived peptides exhibit antimicrobial and antibiofilm activities against methicillin-resistant.

Temporin-GHa (GHa) was cloned from , showing a weak antimicrobial activity. In order to improve its bactericidal efficacy, GHaR6R, GHaR7R, GHaR8R and GHaR9W were designed and synthesized. Compared to the parent peptide, the GHa-derived peptides show potent antimicrobial activities against methicillin-resistant (MRSA), which is the main pathogen with high morbidity and mortality that causes various infections in humans. These peptides exert bactericidal actions on MRSA by permeabilizing the cytoplasmic membranes and damaging membrane integrity. All of the four peptides exhibit excellent stability under harsh conditions, including extreme temperature and salts. Furthermore, they inhibit the formation of biofilm and eradicate mature biofilm of MRSA. The GHa-derived peptides decrease bacterial surface hydrophobicity, autoaggregation and polysaccharide intercellular adhesion synthesis in concentration-dependent manner. Real-time quantitative reverse transcription PCR analysis revealed that the peptides downregulate the expression of adhesion genes involved in biofilm formation. Except for GHaR7R, the other three peptides have low hemolytic toxicity against human erythrocytes. In the presence of human erythrocytes, GHaR7R, GHaR8R and GHaR9W interact with MRSA preferentially. GHaR6R, GHaR8R and GHaR9W show less toxicity toward normal cells HL-7702 and hFOB1.19. These results suggest that the GHa-derived peptides may be promising antimicrobial candidates against MRSA infections.

Temporin-Like Peptides Show Antimicrobial and Anti-Biofilm Activities against Streptococcus mutans with Reduced Hemolysis.

In our previous study, temporin-GHaR (GHaR) showed potent antimicrobial activity with strong hemolytic toxicity. To overcome its weakness, we designed GHaR6R, GHaR7R, GHaR8R, GHaR9R, and GHaR9W by changing the number of positive charges and the hydrophobic surface of GHaR. With the exception of GHaR7R, the hemolytic toxicity of the derived peptides had been reduced, and the antimicrobial activities remained close to the parent peptide (except for GHaR9R). GHaR6R, GHaR7R, GHaR8R, and GHaR9W exhibited a great bactericidal effect on Streptococcus mutans (S. mutans), which is one of the main pathogens causing dental caries. According to the membrane permeation and scanning electron microscope (SEM) analysis, these derived peptides targeted to the cell membranes of planktonic bacteria, contributing to the disruption of the membrane integrity and leakage of the intracellular contents. Moreover, they inhibited the formation of biofilms and eradicated the mature biofilms of S. mutans. Compared with GHaR7R, the derived peptides showed less cytotoxicity to human oral epithelial cells (HOECs). The derived peptides are expected to be the molecular templates for designing antibacterial agents to prevent dental caries.