Glucose addition improves the culture performance of Pacific white shrimp by regulating the assembly of Rhodobacteraceae taxa in gut bacterial community

The family Rhodobacteraceae is a major core bacterial group in the gut of Pacific white shrimp (Penaeus vannamei) and its abundance can be stimulated by the carbohydrates (e.g., glucose) addition in biofloc-based culture systems. However, how glucose addition regulates Rhodobacteraceae assembly at a fine taxonomic resolution and its relationship with shrimp culture performance are unclear. Here, using full-length 16S rRNA gene PacBio sequencing, we explored fine-scale assembly mechanism of gut Rhodobacteraceae regulated by glucose addition. Glucose addition significantly enhanced the growth, survival rate, and feed efficiency of shrimps, and induced Rhodobacteraceae assembly consequently to create a more stable gut bacterial community, reflected by enhanced convergence and network stability as compared to those of the control. Five Ruegeria taxa were identified as potential probiotic candidates for improving shrimp culture performance. Meanwhile, the neutral model showed that positive host selection of gut Ruegeria taxa (primarily R. conchae and R. arenilitoris) from both water and gut metacommunities was enhanced by glucose addition, which stimulated deterministic assembly of gut Rhodobacteraceae. Moreover, differences in assembly processes of Rhodobacteraceae taxa at presumed strain-level within the same species (i.e., R. conchae) were observed, suggesting the necessity of revealing aquaculture bacterial assembly at the finer taxonomic resolution. Collectively, structural equation modeling demonstrated glucose addition improved shrimp culture performance largely by regulating the gut Rhodobacteraceae assembly. Our study provides insights into the assembly of gut Rhodobacteraceae stimulated by a basic regulatory measure in biofloc-based culture systems, holding the practical potential in managing a beneficial microbiota for shrimp culture.