Mechanism of eugenol inhibiting the growth of vegetative cells and spores of Bacillus cereus and its application in rice cakes

Abstract

Recently, natural active substance has been widely concerned and researched because of its potent effect in the control of foodborne pathogen pollution. In this study, we explored the mechanism of eugenol (EL) against Bacillus cereus (B. cereus) and its spores and the potential of EL in controlling the growth of B. cereus in rice cakes. The results of antibacterial activity showed that EL performed potent antibacterial activity against B. cereus (MIC=0.4 mg/mL, MBC=0.8 mg/mL). EL could increase the permeability of cell membrane, increase the leakage of intracellular protein and disturb the balance of ion exchange within bacteria. Molecular docking and competitive fluorescence experiments revealed that EL interacted with DNA through grooving binding. Under the above multiple effects, the normal metabolic activities within bacteria were severely affected and even leading to death. EL treatment resulted in the decrease of multiple toxin synthesis genes (nheA, nheB, nheC, hblC, hblD, hblA, and cytK) expression levels, and significantly reduced the hemolysis activity of toxins through hydrophobic interactions and hydrogen bonding forces. EL was proved to be effective in inhibiting the growth of B. cereus in rice cakes. The inhibition on spore germination and the improvement of spore thermal sensitivity by EL would also provide a valid method for spore control. This study revealed the antibacterial mechanisms of EL against B. cereus and its spores, and laid a theoretical foundation for expanding its application in the control of foodborne pathogens contamination.