Dodartia orientalis L. essential oil exerts antibacterial activity by mechanisms of disrupting cell structure and resisting biofilm

Concerns about the use of synthetic preservatives during food processing and storage have been raised due to their potential side effects on human health and the environment. The antibacterial activities, mechanisms, and chemical compositions of the essential oil of Dodartia orientalis L. which has been long consuming as traditional Chinese medicine against foodborne and spoilage bacteria were investigated as a potential substitute for synthetic preservatives for the first time. Dodartia orientalis L. essential oil (DoEO) exhibited significant antibacterial activities against three foodborne pathogens (Staphylococcus aureus, Escherichia coli, and Salmonella enteritidis). The minimum inhibition concentrations (MIC) of DoEO were 0.5, 1, and 2 μL/mL while the minimum bactericide concentrations (MBC) were 1, 2 and 4 μL/mL against the strains of S. aureus, E. coli, and S. enteritidis, respectively. Alkaline phosphatase (AKP) leak assay revealed that DoEO caused the destruction of structure and function of cell wall. Nucleic acids leak, potassium ions leak, and propidium iodide (PI) assays showed that DoEO aroused the stimulating release of intracellular nucleic acids and potassium ions by damaging membrane integrity. Scanning electron microscopy (SEM) observation further verified that DoEO could exert bactericidal activity via disrupting cell walls and membranes. On the other hand, XTT and crystal violet (CV) experiments indicated that DoEO was able to prevent fresh biofilm formation and destroy preformed biofilm through decreasing biofilm biomass and biofilm cellular activity. Bacterial surface hydrophobicity assay revealed that DoEO was capable of reducing the adhesive capacity of the strains, belonging to its antibiofilm mechanisms. Furthermore, the main chemical compositions of DoEO were identified by gas chromatography-mass spectrometry analysis (GC-MS). Therein, antibacterial components were classified and analyzed. All results above confirmed that the antibacterial activity of DoEO was mainly aroused by disrupting cell structure and resisting biofilm, which indicated that DoEO was expected to be an efficient functional ingredient with great potential applications in food preservative.