16S rRNA and transcriptome analysis of the FOS-mediated alleviation of Aeromonas hydrophila-induced intestinal damage in Megalobrama amblycephala

This study was conducted to elucidate the effects of FOS that alleviate Aeromonas hydrophila-induced intestinal damage. The results showed that A. hydrophila disrupted the intestinal structure and increased intestinal permeability, causing abnormalities in mucosal pathology. Additionally, A. hydrophila induced an imbalance in the intestinal flora and disturbed its stability. Dietary FOS ameliorated the injury to the intestinal structure of fish, but also in part improved the condition of the intestinal tight junction complex. Transcriptomic analysis showed that 120 genes were up-regulated and 320 genes were down-regulated. The intestinal immune network for the IgA production signalling pathway was enriched following A. hydrophila infection, and the change in the FOS group was mainly in the Tight junction signalling pathway. Similarly, dietary FOS reduced the disruption of the intestinal microbiota induced by A. hydrophila and improved the intestinal microbiota's stability; FOS was also partially implicated in the upregulation of Tight junction and Adhesion junction pathways by transcriptomic analysis. After further analysis, it was found that fish fed FOS had upregulated expression of genes related to apoptosis, antigen presentation, and the T-cell-mediated immune response in the intestine compared with those in the A. hydrophila group, which may be related to changes in the intestinal microbiome.