Multi-Target Bactericidal Mechanisms of Cinnamon Essential Oil Against Xanthomonas euvesicatoria: Transcriptomic Insights into Severe Metabolic Suppression and Divisome Arrest

While cinnamon essential oil (CEO) is increasingly recognized as a potent natural antimicrobial, its precise multi-target mechanisms against the destructive agricultural pathogen Xanthomonas euvesicatoria remain unclear. This study comprehensively elucidated the physiological, biochemical, and transcriptomic responses of X. euvesicatoria 173 to CEO-induced stress. We investigated its antibacterial efficacy and specific modes of action using microdilution assays, scanning electron microscopy, biochemical viability tracking, and RNAseq. CEO exhibited robust dose-dependent antibacterial activity, with a minimum inhibitory concentration of 400 mg/L and a half-maximal effective concentration (EC50) of 164 mg/L. Analyses revealed that CEO severely compromised cell membrane integrity, leading to a rapid 100-fold increased hypersensitivity to osmotic stress and significant suppression of biofilm formation. Furthermore, sub-lethal CEO exposure induced a severe energy crisis by disrupting membrane-dependent ATP synthesis-measured as a significant reduction in F1F0-ATPase activity-and caused abnormal cellular elongation, indicating cell division arrest. These distinct phenotypes were supported by comparative transcriptomics at the sub-lethal EC50 dose, which revealed 209 highly significant differentially expressed genes (|log2FC| > 3.321). CEO massively downregulated genes associated with the electron transport chain and core energy metabolism (nuo, ndh, cyd, and cyo operons), the ftsZ divisome network, and biofilm-associated type IV pilus and chemotaxis. Conversely, oxidative stress defense genes (kat and ahpD) were upregulated. In conclusion, CEO exerts its bactericidal activity through a synergistic, multi-target action-simultaneously dismantling membrane energetics, inducing severe metabolic suppression, and repressing vital developmental architectures. These findings highlight the significant potential of CEO as a sustainable, resistance-breaking biopesticide for crop protection.