Antimicrobial activity and mechanism of limonene against Staphylococcus aureus

Abstract In this study, inhibitory effect of limonene on Staphylococcus aureus (S. aureus) and its antibacterial mechanism was explored, respectively. The results showed that limonene effectively inhibited bacterial growth at a minimum inhibitory concentration (MIC) of 20 ml/L. Scanning electron microscopy (SEM), the reduction of AKP activity and fluorescence microscope observation confirmed that limonene caused the destruction of the cell morphology and cell wall integrity of S. aureus. The reduction of MFI in fluorescein diacetate staining experiment and leakage of biological macromolecules (nucleic acids and proteins) indicated that limonene damaged the cell membrane and increased membrane permeability. Besides, the reduction of membrane potential (MP) further confirmed that the damage to membrane and the reduction of respiratory metabolic activity. Furthermore, the respiratory depression test confirmed that the pathway of limonene affecting the respiratory metabolism of S. aureus is TCA pathway, followed by EMP. In addition, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), ATPase (T‐ATPase, Na+‐K+‐ATPase, Ca2+‐Mg2+‐ATPase), and ATP concentration demonstrated that limonene could result in a slowdown of metabolism and metabolic dysfunction, thus inhibiting ATP synthesis.