Biofloc-based bacterial community forms an ecological barrier for resisting Vibrio parahaemolyticus infection in shrimp

Biofloc system (BFS) is a practical method to improve shrimp health via manipulating microbial community. However, the contribution of bacterial communities regulated by BFS in enhancing disease resistance is currently unclear. Here, a cross-combination experiment was conducted using rearing water and shrimp from control and BFS to elucidate the roles of bacterial communities in resisting Vibrio parahaemolyticus infection. The results showed that shrimp cultured in BFS were more resistant to V. parahaemolyticus , and the combinations of shrimp from control (CS) with rearing water from BFS (BW), and shrimp from BFS (BS) with rearing water from control (CW) could all significantly increase the shrimp resistance to V. parahaemolyticus , compared to CW+CS. Following infection, the gut bacterial community in BW+CS and BW+BS groups exhibited less variation in similarity, and higher relative abundances of taxa from Rhodobacteraceae . SourceTracker analysis suggested that shrimp cultured with BW had a reduced contribution of Vibrionaceae from rearing water to the gut. Strains corresponding to four key differential OTUs were isolated from BFS to establish two synthetic communities, which offered a protection to shrimp against V. parahaemolyticus infection. Our study showed that bacterial communities in BFS, especially in rearing water, were important for shrimp to resist pathogen. • BFS protected shrimp from Vibrio by shaping a more stable gut bacterial community. • Shrimp combined with biofloc water (BW) reduced Vibrionaceae transfer from rearing water to gut. • Shrimp combined with BW enriched some key taxa like Pseudoruegeria and Phaeobacter , related to Vibrio resistance. • The corresponding strains of these key taxa were isolated from BFS. • Combination of three corresponding strains protected shrimp against Vibrio infection.