Gnotobiotic models: Powerful tools for deeply understanding intestinal microbiota-host interactions in aquaculture

Intestinal microbiota plays profound roles in host nutrition, physiology, and evolution. The development of DNA sequencing technologies has increased dramatically research on fish intestinal microbiota. However, most studies conducted so far have focused on the microbial structure and diversity. Studies targeting the exact function of commensal microbes in aquatic animals are still scarce, which limits the application of microbiota related knowledge in aquaculture. Gnotobiotic models (animals cultured in axenic conditions or with defined microbial lineages) are excellent tools for identifying the molecular interactions between intestinal microbiota and host, which drive studies of microbiota from correlation to causality in mammals. In recent decades, gnotobiotic fish models have been established and applied in aquaculture research. This review summarizes the colonization conditions in gnotobiotic zebrafish model and its application in understanding intestinal microbiota-host interactions in aquaculture. Furthermore, methods and research progress on other gnotobiotic models including freshwater and marine fishes, molluscs and crustaceans are also discussed. Application of gnotobiotic models in aquaculture has deepened our understanding of the relationship between the host and intestinal microbiota, which will facilitate the modulation of intestinal microbiota for production of healthy animals and sustainable development of aquaculture.