Fig. 4

Gut microbiota are the basis of B₁₂ protection against A. hydrophila infection in zebrafish. a The experimental design. (i) The zebrafish were fed a basic diet supplemented with/without vitamin B₁₂ (200 μg/kg diet per day) for 28 days (Group B/CK), respectively, and then bath infected with A. hydrophila strain at a concentration of 1 × 10⁸ CFU/mL (Group TB/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 AB/ACK), and then received the same treatments as (i) (Group TAB/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, d Aeromonas load (Aero gene copies/g of fish tissues) in fish tissues (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. e, f Linear correlation between the B₁₂ content and pathogen load in liver and kidney, respectively. Linear correlation was performed with Pearson’s linear correlation