Aeration remodels the gut bacterial community and co-metabolic profile in sea cucumber (Apostichopus japonicus)

Aeration is a crucial method for disrupting water stratification and enhancing the living conditions of the cultured species in the process of pond aquaculture. The mechanism by which sea cucumber (Apostichopus japonicus) gut microbiota and metabolism in response to aeration are poorly understood. In the present study, we exposed the A. japonicus to aerated ponds and non-aerated ponds for 60 days. To address the aeration effect on gut microbiota and metabolism, the gut bacteria and metabolites of A. japonicus was assessed using the 16S rRNA sequencing and metabolomics technology. The results showed that the diversity and abundance of the gut microbiota of A. japonicus increased significantly after aeration, and the aeration treatment significantly changed the structural composition of the gut microbiota of A. japonicus. Among them, the relative abundance of Vibrio decreased by 12.86 %, and the relative abundance of Photobacterium and Ruegeria both increased by more than 500 %. A total of 102 differential metabolites were screened by metabolomics, of which 70 metabolites were significantly up-regulated and 32 metabolites were significantly down-regulated. Further metabolic pathway enrichment analyses revealed that aeration affects arachidonic acid metabolism, linoleic acid metabolism, and inflammatory mediator regulation of TRP channels through pathways that promote the accumulation of diglyceride and phosphatidylcholine. Through the Pearson correlation analysis found that Photobacterium, Ruegeria are positively correlated with anti-inflammatory substances such as phosphatidylcholine, l - pyroglutamic acid, Acetyl - dl – carnitine and betaine, Vibrio and Tepidibacter showed a significant negative correlation with them. The results suggested that aeration improves the physiological state of the organism by affecting the gut microbial composition and host metabolic state of A. japonicus indirectly. This study provides a theoretical basis for the healthy and enhanced cultivation of A. japonicus.