Integrated gut microbiome and serum metabolomics analysis to reveal seawater adaptation strategy in Chinese sturgeon

The structure of the fish gut microbiota changes with variations in the living environment, including salinity, which has been regarded as the most important environmental change factor in the transition of Chinese sturgeons, Acipenser sinensis , from river to sea. Therefore, this study investigated the characteristics and metabolic functions of the gut microbiota of Chinese sturgeons in response to changes in salinity (from freshwater to seawater). We conducted a seawater acclimation trial on juvenile Chinese sturgeons and analyzed their gut microbiota and serum metabolites using 16S rRNA gene sequencing and widely targeted metabolomics. Our findings indicate that environmental salinity can influence gut microbiota composition and serum metabolites. Specifically, 16S rRNA analysis revealed enrichment of Bacillaceae, Ruminococcaceae, Eimeria praecox , and Rhodobacteraceae in individuals exposed to hypertonic salinity. Additionally, a widely targeted metabolomics approach showed the upregulation of 123 metabolites and downregulation of 30 metabolites, with significantly different metabolites primarily involved in carbohydrate metabolism. Furthermore, correlation analysis revealed a relationship between these metabolites and the bacterial communities, particularly Ruminococcaceae and Prevotellaceae. Our results provide insights into the seawater adaptation strategies of Chinese sturgeons, suggesting that alterations in the abundance of specific gut microbiota can influence carbohydrate metabolism and enhance carbohydrate utilization to meet energy requirements during seawater adaptation. These insights may help develop effective ex situ conservation strategies for this species. • Freshwater artificially cultured Chinese sturgeons were acclimated in seawater. • Chinese sturgeon gut microbiota and serum metabolites were altered by salinity. • Altered serum metabolites showed significant correlations with gut microbiota. • Carbohydrate metabolism played crucial roles in the seawater acclimation. • Results provide insights into seawater adaptation strategy in Chinese sturgeon.