Fig. 1

Microbiota is essential to protect fish against A. hydrophila infection after B. velezensis 1704-Y supplementation. a The experimental design. (i) The zebrafish were fed a basic diet supplemented with/without B. velezensis 1704-Y (1 × 10⁷ CFU/g diet) for 28 days (Group Y/CK), respectively, and then bath infected with A. hydrophila AH2006-3 J at a concentration of 1 × 10⁸ CFU/mL (Group TY/TCK); (ii) The zebrafish were fed a diet containing an antibiotic mix (120 mg/kg metronidazole, 120 mg/kg neomycin sulfate and 60 mg/kg vancomycin) for 7 days (Group AY/ACK), and then received the same treatments as (i) (Group TAY/TACK). b Kaplan–Meier graph of the zebrafish survival after bath infection with A. hydrophila. * indicates significant difference (P < 0.05) between different groups. c–e 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 above the bars