Abstract: This study aimed to elucidate the intracellular mechanism of action of antimicrobial peptide F1 on Staphylococcus aureus. The binding of the genomic DNA of S. aureus to antimicrobial peptide F1 was investigated with gel retardation, and the competitive intercalation of F1 and ethidium bromide (EB) into the genomic DNA were analyzed by fluorescence spectroscopy. The influence of F1 on the synthesis of protein in S. aureus was determined by Coomassie brilliant blue method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The inhibition of β-galactosidase and nonspecific esterase activities of S. aureus cells by the antibacterial peptide was measured using o-nitrophenyl β-D-galactopyranosiden (ONPG) and di-O-acetylfluorescein (FDA), respectively. Finally, the changes in the cell cycle of S. aureus after being treated by F1 were monitored with flow cytometry. The results showed that F1 bound with DNA and could weaken the fluorescence intensity of EB-DNA complex, hindering the expression of genetic information of S. aureus. Besides, the protein biosynthesis of S. aureus was also inhibited, which was further proven by the measured activities of two intracellular enzymes, β-galactosidase and non-specific esterase. Therefore, F1 could lead to the aberration of the intracellular enzyme system and metabolic pathways of S. aureus, and block the DNA synthesis phase of the cell cycle of S. aureus.

Key words: antimicrobial peptide F1, Staphylococcus aureus, intracellular mechanism of action, cell cycle