Study On Antibacterial Activity And Mechanism Of Antimicrobial Peptide P26

Antimcrobial peptides(AMPs)are a class of small polypeptides encoded by specific genes.They are widely distributed in various organisms and are important molecules in organism immunity system.In this study,AMP P26 was used to determine its minimum bactericidal concentration(Minimal bactericidal concentration,MBC)and minimum inhibitory concentration(Minimal inhibitory concentration,MIC)against several bacteria.The membrane action and non-membrane actiosn of P26 were systematically carried out.We also evaluated the antimicrobial effect of P26 on chilled meat The main research contents were as follows:(1)P26 has 6 amino acids with a molecular weight of 496.9[M+2H]2+ Da and a net charge of 3.0.The hydrophilic residue ratio is 50%.P26 has an MBC of 100-300 μg/mL and an MIC of 25-200 μg/mL for the four test bacteria(Staphylococcus aureus,Listeria monocytogenes,Escherichia coli and Salmonella enterica).The MBC and MIC of P26 against Gram-positive bacteria L.monocytogenes were 100 μg/mL and 25 μg/mL,respectively.(2)The results of bacterial cell membrane permeability and phosphorus ion leakage showed that P26 can cause increased membrane permeability and concentration of inorganic phosphorus of the four tested bacterial cells compared with normal bacteria.The results of transmission electron microscopy showed that after the bacteria were treated by P26,the cell membrane of the bacteria also deformed and wrinkled.There was more obvious leakage of substances in the cells,the reduction in electron density,unevenness,and the formation of voids cavity.After P26 treatment,slight damage and holes were seen in the bacterial cell membrane of L.monocytogenes.Scanning electron microscopy showed that the cell surface of L.monocytogenes after P26 treatment was broken and damaged,and a slight fracture surface appeared.P26 can only bind to bacterial DNA at a higher concentratior,and the ability of this binding has a certain concentration dependence.(3)After P26,Nisin and Chlorampheniccol(CL)were incubated with L.monocytogenes for 1 h,the adhesion rate of L.monocytogenes was reduced.In terms of inhibiting the formation of bacterial biofilms,P26 inhibited 63.76%biofilm formation of L.monocytogenes at 25 μg/mL,and only 7.57%of L.monocytogenes biofilm remained at 200 μg/mL.As the concentration of P26,Nisin and CL increases,the better the destructive effect on the formed biofilm of L.monocytogenes.The disturbing rate of P26 to L.monocytogenes biofilm reached 62.05%at 200μg/mL.(4)Under different salt concentrations(NaCl,CaCl),compared with the basic medium,the higher the salt concentration,the lower the antibacterial activity of P26 against L.monocytogenes and S.enterica.Serum can affect the antibacterial activity of P26.As the serum concentration increases,the antibacterial activity of P26 decreases.P26 has higher antibacterial activity in weakly alkaline environments than in weakly acidic conditions.(5)Based on the indexes of microorganism,pH and TVB-N,the effect of P26 on the preservation of chilled meat was evaluated.The results showed that the chilled meat treated with P26 had doubled the preservation time compared with the control group.Compared with the treatment of P26 and EDTA alone,at the same concentration,the compounding of P26 and EDTA has a better effect on the preservation of chilled meat.This study will theoretically help us to understand the antibacterial activity and mechanism of antibacterial peptide P26,and provide technical support for the development of P26 as a peptide preservative in application.