Gut microbiota remodeling and immune gene modulation by Semiliquidambar cathayensis protect Misgurnus anguillicaudatus against Aeromonas hydrophila: integrative transcriptomic and 16S rRNA analysis

This study aims to explore the regulatory mechanism of Semiliquidambar cathayensis extract on the immune stress induced by Aeromonas hydrophila in Misgurnus anguillicaudatus . Through transcriptomics and 16S rRNA sequencing techniques, the changes in gene expression profiles of M. anguillicaudatus muscle tissues and the structure of the intestinal microbiota were analyzed separately. The transcriptomic results showed that a total of 1,080 differentially expressed genes were screened out after S. cathayensis treatment, among which 509 were upregulated and 571 were downregulated. GO enrichment analysis indicated that these genes mainly participated in cellular processes, biological regulation, and stress responses. KEGG enrichment analysis revealed that they were significantly enriched in immune-related pathways such as antigen processing and presentation, complement and coagulation cascade reaction, and phagosome. The 16S rRNA sequencing results showed that S. cathayensis treatment significantly reshaped the intestinal microbiota structure. The dominant bacterial genera changed from Lactococcus and Myroides to Elizabethkingia, with Elizabethkingia meningoseptica accounting for an absolute majority in the treatment group, with an abundance of up to 61.70%. The integrated analysis indicated that S. cathayensis may affect the expression of host immune-related genes by regulating the abundance of specific bacterial communities (especially the Elizabethkingia genus), thereby alleviating the immune stress induced by A. hydrophila . This study provides a theoretical basis for the development and application of S. cathayensis as an aquatic immune enhancer, and also offers a new research perspective for exploring the immune regulatory effects of traditional Chinese medicine through ‘microbiota-host’ interaction.