Integrated Transcriptomic and Metabolomic Analyses Reveal the Antibacterial Mechanism of Isocorydine against Mycobacterium bovis

Xia WangWeichao MaYijun YuanXiang GaoTianyu ZhaoPeng WangYanmei Liu^*Tingpu Wang^*

• Tianshui Normal University, Tianshui, China

Mycobacterium bovis, the causative agent of zoonotic tuberculosis, poses a serious threat to public health and agriculture. This study investigates the antibacterial activity and mechanism of action of isocorydine (ICD), a natural alkaloid from Dicranostigma leptopodum (Maxim.) Fedde (DLF), against M. bovis. We found that ICD exhibited potent antibacterial activity with a minimum inhibitory concentration (MIC) of 400 μg/mL. Phenotypic analyses demonstrated that ICD disrupted cell wall and membrane integrity, leading to ion leakage, altered extracellular pH, reduced total lipid content, and severe ultrastructural damage. To elucidate the global response, transcriptomic and metabolomic profiles of M. bovis under sub-inhibitory ICD stress were analyzed. Transcriptomics revealed 66 differentially expressed genes, with significant upregulation of efflux pump systems and their associated TetR family transcriptional regulators. Metabolomics identified 1,158 differential metabolites, indicating a profound metabolic rewiring characterized by depletion of central carbon metabolites and accumulation of fatty acids, suggesting a dysregulated state of energy metabolism. Pathway analysis highlighted significant alterations in starch/sucrose metabolism, ABC transporters, and fatty acid biosynthesis. Our results demonstrate that ICD exerts its antibacterial effect primarily by targeting the cell envelope of M. bovis, causing membrane disruption and energetic stress, to which the bacterium responds by activating efflux pumps and reprogramming its metabolism. This multi-omics study reveals the potential of ICD as an anti-mycobacterial agent and provides novel insights into the adaptive strategies of M. bovis under phytochemical stress.