Effect of the gut core microbiota Cetobacteriumon the growth, physiology, and nutritional metabolism of Nile tilapia (Oreochromis niloticus)

As a gut core microbiota in tilapia, Cetobacteriumlikely plays an essential nutritional role in the gut. We performed a feeding experiment to identify its function in the growth, physiology, and nutritional metabolism in Nile tilapia (Oreochromis niloticus). Tilapia were fed either a control diet (CK) or a CetobacteriumNK01-supplemented diet (1 × 107CFU/g diet) (NK) for a period of 42 days. Analysis of growth indices, serum insulin, glucose and triglyceride (TG) levels, carbohydrate content in the gut, and amino acid levels in the serum were conducted. Additionally, we examined the transcriptome of the liver and the metabolome of the serum in tilapia. Our results showed that dietary supplementation with NK01 significantly improved carcass ratio, increased levels of insulin and amino acids in the serum, and reduced serum glucose and TG levels as well as gut carbohydrate content. Furthermore, analysis of the liver transcriptome and RT-qPCR data indicated a decrease of genes expression of fatty acid synthesis (SREB 1c, ACCα, and FAS) with NK01 supplementation feeding group. Metabolomics analysis revealed enhanced protein and amino acid metabolism in the serum of tilapia with NK01 supplementation feeding group. The relative abundance of the genus Romboutsiain the gut content of tilapia in the NK group decreased, and this was found to be positively associated with dietary sugar levels. Overall, our findings suggest that appropriate supplementation (1 × 107CFU/g diet) with NK01 can serve as an effective nutritional strategy to enhance the metabolism and overall health of tilapia in aquaculture.