Fig. 2
Resistance to A. hydrophila infection is conferred by Cetobacterium somerae. a Shannon index comparison among the different groups. The zebrafish in Group Y and CK were fed a basic diet supplemented with/without Bacillus velezensis 1704-Y (BV1704-Y), respectively, and then bath infected with A. hydrophila 2006-3 J (AH2006-3 J) at a concentration of 1 × 108 CFU/mL (Group TY/TCK). b A principal coordinate analysis (PCoA) based on Bray–Curtis distance from the different groups (Y, CK, TY, and TCK) (ANOSIM R = 0.647, P = 0.001). c Relative abundance of the top 20 genera in the fish gut from the different groups. d Discriminative biomarkers identified by linear discriminant analysis effect size (LEfSe) with logarithmic LDA score > 3.0. e Relative abundance of selected different taxa. Data are expressed as box plot. ∗ P < 0.05, ∗  ∗ P < 0.01 by Mann–Whitney U test with Bonferroni-adjusted P-values. f Heat map of Pearson’s correlation coefficients between the top 20 genera and the diets (Y:CK, left) or infection status (CK:TCK, right). Dark red indicates a stronger positive correlation, dark blue indicates a stronger negative correlation, and white indicates no correlation. Black asterisk (*) means FDR-corrected P-value < 0.05. g The experimental design. The zebrafish were fed a basic diet supplemented with/without Cetobacterium somerae CS2105-BJ (1 × 107 CFU/g diet) for 28 days (Group Ceto/CK), and then bath infected with AH2006-3 J at a concentration of 1 × 108 CFU/mL (Group TCeto/TCK). h Kaplan–Meier graph of the zebrafish survival after bath infection with AH2006-3 J. i Cetobacterium load (gene copies/g of fish gut) in the gut of fish sampled prior to bath infection. j Aeromonas load (Aero gene copies/g of fish tissues) in fish tissues (gut, liver and kidney) sampled prior to bath infection or at 10 days post-infection. Significant differences (P < 0.05) between different groups are indicated with different lowercase letters