黄芩苷抑制嗜水气单胞菌生长的作用机制研究

To explore the mechanism of action of baicalin in inhibiting the growth of Aeromonas hydrophila. By analyzing the effects of baicalin on the growth, morphology, and transcriptome data of A. hydrophila, key candidate genes for its inhibition were identified. Specifically, the minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC) of baicalin against A. hydrophila were determined using the serial dilution method. The bacteria were inoculated into liquid media containing different concentrations of baicalin, and the OD600 values were measured to construct growth curves. The morphological changes of the bacteria were observed using transmission electron microscopy. RNA was extracted from the collected bacteria for high-throughput transcriptome sequencing. Differential genes were screened using the threshold of |log2(Fold change)|≥1 and P≤0.05, and key genes were identified through GO annotation and KEGG functional enrichment analysis. The transcriptome sequencing results were verified using RT-qPCR. The MIC and MBC of baicalin against A. hydrophila were both 7.81 mg/mL. Baicalin at a concentration of 1/2 MIC prolonged the time for the bacteria to enter the stationary phase and had a certain inhibitory effect on bacterial growth. Baicalin at a concentration of 1 MIC significantly inhibited the growth of A. hydrophila. Transmission electron microscopy revealed that the surface of the bacteria treated with baicalin was not smooth, the edges of the cell wall were rough, and the normal structure of the bacteria was destroyed, indicating that baicalin could disrupt the structural integrity of A. hydrophila. The transcriptome sequencing results showed that after baicalin acted on the bacteria, a total of 908 genes exhibited differential expression to varying degrees, among which 556 genes were upregulated and 352 genes were downregulated. The differentially expressed genes were significantly enriched in the two-component system, phosphotransferase system, and amino acid synthesis and metabolism-related coding genes of A. hydrophila. GO functional analysis revealed that the differentially expressed genes were involved in processes such as cellular composition, extracellular region, and catalytic activity. KEGG enrichment analysis indicated that the differentially expressed genes were mainly enriched in pathways related to protein synthesis, genetic information processing, and the biosynthesis of branched-chain amino acids. The results of the RT-qPCR experiment demonstrated the high accuracy of the transcriptome data. Animal experiments showed that baicalin not only enhanced antioxidant capacity but also significantly regulated the expression of inflammation-related genes such as spleen IFN-γ and TNF-α, effectively improving oxidative stress and inflammatory states in the body. Baicalin can significantly inhibit the growth of A. hydrophila, disrupt the structural integrity of the bacterial cell, and alter the physiological and biochemical functions and virulence of A. hydrophila by affecting extracellular transport metabolism, two-component systems, and related amino acid synthesis and metabolism signaling pathways. Furthermore, it can alleviate oxidative stress and inflammatory responses in infected animals.