Antimicrobial Activity Of Pleurocidin And New Design Peptide Against Cariogenic Bacteria

1、Antimicrobial and antibiofilm activity of pleurocidin againstcariogenic microorganismsPleurocidin, produced by Pleuronectes americanus, is an antimicrobialpeptide that exerts broad-spectrum activity against pathogenic bacteria and fungi.Moreover, pleurocidin shows less hemolysis and is less toxic than other naturalpeptides. In the present study, we investigated whether pleurocidin is aneffective antibiotic peptide against common cariogenic microorganisms andperformed a preliminary study of the antimicrobial mechanism. We assayedminimal inhibitory concentration (MIC), minimal bactericide concentration(MBC) and bactericidal kinetics and performed a spot-on-lawn assay. TheBioFlux system was used to generate bacterial biofilms under controllable flow.Fluorescence microscopy and confocal laser scanning microscopy (CLSM) wereused to analyze and observe biofilms. Scanning electron microscopy was used toobserve the bacterial membrane. MIC and MBC results showed that pleurocidin had different antimicrobial activities against the tested oral strains. Althoughcomponents of saliva could affect antimicrobial activity, pleurocidin dissolved insaliva still showed antimicrobial effects against oral microorganisms.Furthermore, pleurocidin showed a favorable killing effect against BioFlux flowbiofilms in vitro. Our findings suggest that pleurocidin has the potential to killdental biofilms and prevent dental caries2Design and antimicrobial activity of new peptides againstcariogenic microorganismsFish possess a strong innate immune system that acts as the first line ofdefense against a broad spectrum of pathogens. We have demonstrated thatα-helix linear cationic peptide pleurocidin is sensitive to cariogenic bacteria,fungi, and have antibiofilm of Streptococcus mutans biofilms. However,pleurocidin is composed by25amino acid residue, and synthetic cost is highand has the poor ability to penetrate the entire bacterial biofilm, therefore thedevelopment of new peptide is even more necessary.In this study, GW18, activity centers of pleurocidin, was confirmed and aseries of new peptides were designed. Pc1, pc8, pc9, pc11and pc12, congenersof pleurocidin, had antibacterial ability against several oral microorganisms. Pc9had the best antibacterial activity, while pc12was the shortest peptide..Hydrophobicity and the length of the peptide are related to antibacterial ability.Duo to the short time killing effect of, it was suggested that pc12was a ‘rapidkill’peptide.3The antibacterial mechanism and the cytotoxic of the new designed peptides Pc9, Pc12Many peptides are cytotoxic and even have a strong hemolytic effect. Theideal peptide does not have any side effects or allergic reactions of the immunesystem. In this part of the experiment, electron microscopy was used to observethe membrane damage of pc9, pc12and cell experiments was taken to study thecytotoxic of new designed peptides.Electron microscopy showed that after exposed under Pc9and Pc12,membrane of Streptococcus mutans and Streptococcus sanguis is damaged bythe peptide. The bacteria lose their original shape, and transmembrane poreappeared. The pore diameter is about10nm, the formation of ion channels in thebacterial surface caused the outflow of the bacterial contents, resulting in thedeath of the bacteria. HGFs were treated with8xMIC of pc9and pc12. Aftercultured for2hours, there was some influence to the cell. However, shortexpose (5minutes,1hour) showed no statistically significant difference to thecontrol group. However, pc12had the ability to kill Streptococcus mutans in onehour. Therefore, our findings suggest that pc9has the potential to prevent dentalcaries...