Mechanisms of antifungal activity of ehimensin F6 produced by Paenibacillus ehimensis HD against Penicillium expansum

Abstract

Penicillium expansum is a common spoilage fungus in postharvest fruits that can lead to fruit rot and health damage. This study aims to identify the antimicrobial mechanism of antimicrobial peptide named ehimensin F6 from Paenibacillus ehimensis HD against P. expansum. The ehimensin F6 was applied to the fresh mycelia of P. expansum at varying concentrations of 0MIC, 0.5MIC, 1MIC, and 2MIC (final concentration) to evaluate its effects on the cell wall, cell membrane, genomic DNA, and proteins of P. expansum mycelia. In addition, cherries were divided into four groups: treated with sterile water, low/high concentrations of ehimensin F6, or potassium sorbate. All were inoculated with P. expansum, stored at 25 °C for 5 days, and evaluated for antifungal effects by measuring lesion diameters and viable counts of P. expansum. The results demonstrated that ehimensin F6 obviously inhibited the growth of P. expansum in a dose-dependent manner. Fluorescence spectroscopy analysis indicated that ehimensin F6 destroyed the integrity of the fungal cell membrane and increased cell membrane permeability, leading to membrane potential dissipation and K⁺ leakage. Electron microscopy observations revealed obvious significant morphological alterations in P. expansum mycelia, including structural damage, deformation of hyphae, and a reduction in cytoplasmic density. Transcriptomics and proteomics analyses showed that ehimensin F6 affected ergosterol biosynthesis pathway, DNA replication, rnhA and RPB1 genes expression in RNA transcription, amino acid and pyruvate metabolism. Ehimensin F6 effectively inhibited the growth of P. expansum in cherries. These results indicated that ehimensin F6 inhibited the growth and metabolism of P. expansum through many different pathways, and ehimensin F6 had great potential as a bio-preservative to improve food safety.