Antimicrobial Mechanism of Antimicrobial Peptide from Paenibacillus ehimensis against Candida albicans Biofilms

This study investigated the inhibitory effect of antimicrobial peptide from Paenibacillus ehimensis on the biofilms of Candida albicans by the microdilution and time-kill curve assays. Microscopic observation was conducted to assess the impact of the peptide on the formation of C. albicans germ tube and hyphae. Additionally, the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay was employed to investigate the influence on the formation of C. albicans biofilms, pre-formed biofilms, and the clearance rate of mature biofilms. Fluorescent probes were utilized to observe the alteration in the structure of biofilms and the status of intracellular fungal entities. The number of viable cells in biofilms was measured by the spread plate method, and real-time polymerase chain reaction (PCR) was employed to determine the expression levels of genes associated with biofilm formation. The results showed that the minimum inhibitory concentration of the antimicrobial peptide against C. albicans was 8.28 AU/mL. This peptide reduced the rate of germ tube formation in C. albicans, and prevented the formation of hyphae, making it exist in the form of yeasts. Furthermore, the antimicrobial peptide influenced both the formation and eradication of biofilms and disrupted the structural integrity of biofilms after a short duration, leading to damage and even death of C. albicans, and reducing cell counts in biofilms. The antimicrobial peptide reduced the expression levels of multiple genes related to biofilm formation (such as ALS1, ALS3, HWP1, EFG1, ECE1 and UME6), therefore inhibiting biofilm formation. The above findings demonstrated that antimicrobial peptide effectively inhibited the biofilm formation, mature biofilm clearance and the expression of biofilm-forming genes in C. albicans. This study lays a theoretical foundation for the development of novel antimicrobial agents against C. albicans and provides a basis for the prevention and control of foodborne pathogen contamination to ensure food quality and safety.