Abstract: Antimicrobial peptide P-1 from Bacillus pumilus HN-10 has strong antifungal activity against Trichothecium roseum, but its mechanism of action remains unclear. In this study, we investigated this topic from the perspectives of cell membrane permeability, protein synthesis and nucleic acid synthesis. Firstly, the effect of antimicrobial peptide P-1 on the membrane permeability of T. roseum was studied by measuring the release of macromolecules and electrical conductivity. Secondly, the effect on protein synthesis was studied by measuring the expression of intracellular and intracellular proteins through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Finally, in order to prove whether nucleic acid synthesis was inhibited by antimicrobial peptide P-1, agarose gel retardation assay was performed and the competitive binding of antimicrobial peptide P-1 with ethidium bromide (EB) to T. roseum DNA and RNA contents were analyzed by fluorescence spectroscopy. The results showed that the antimicrobial peptide P-1 could increase the membrane permeability of T. roseum, leading to leakage of intracellular electrolytes and macromolecules. Meanwhile, T. roseum protein synthesis was inhibited, especially for proteins with molecular masses between 43.0 and 97.4 kDa. The antifungal peptide showed no DNA gel retardation, but it could compete with EB for binding to DNA and inhibit nucleic acid synthesis, resulting in fungal metabolism disorder and abnormal protein expression and eventually exerting antimicrobial activity.

Key words: antifungal peptide P-1, Trichothecium roseum, membrane permeability, protein synthesis, nucleic acid synthesis