Sucrose-based biofloc system promotes the enrichment of specific gut bacterial taxa to enhance disease suppression in shrimp (Penaeus vannamei)

Abstract

Sucrose-based biofloc system could facilitate the growth and fitness of shrimp (Penaeus vannamei) by regulating the gut bacterial community. However, little is known about the specific taxa enriched by sucrose-based biofloc system that could improve shrimp health. Here, we investigated the influences of sucrose-based biofloc system on the diversity, structure, and function of the shrimp gut bacterial community. Sucrose-based biofloc system enhanced the observed species and shannon index of the gut bacterial community, and altered the bacterial community compositions by aggrandizing the relative abundances of Amaricoccus, Demequina, and Microbacterium, and decreasing the abundances of potential pathogens belonging to Mycoplasmataceae. The relative abundances of three key operational taxonomic units (OTUs), Demequina OTU465, Microbacterium OTU778, and Amaricoccus OTU 3213 accounted for >50% contributions to shrimp growth and survival rate. Sucrose-based biofloc system positively improved the bacterial community functions involved in amino acid metabolism, metabolism of terpenoids and polyketides, and carbohydrate metabolism. These improved functions were also positively associated with these key OTUs, further implying that they might be key for shrimp health. Finally, the corresponding strains of these key OTUs were isolated to construct a synthetic community, which showed significantly promotive role in shrimp growth and resistance against pathogen challenge. These results not only help us understand the role of sucrose-based biofloc system in improving shrimp fitness better but also provide a reference for suppressing disease occurrence through the use of bacterial inocula.