Disturbance in the homeostasis of intestinal microbiota by a high-fat diet in the rice field eel (Monopterus albus)

Abstract Intestinal microbiota plays crucial roles in nutrient uptake and contributes to obesity in aquatic animals, although the association between intestinal microbiota and obesity remains unclear. In this study, high-throughput sequencing was employed to determine the composition, interspecific interactions, and potential function of the microbial community in the intestine of rice field eel ( Monopterus albus ) fed with basal diet (Control group, 6.30% lipid) or high-fat diet (HF group, 12.11% lipid). The high-fat diet decreased species richness, accompanied by a significant reduction in the diversity of intestinal microbiota, and significantly increased the relative abundance of Fusobacteriia (classified as Cetobacterium ), concurrent with a significant reduction in Clostridia (classified as Clostridium ) in the eel. However, the eels in both groups shared the same dominant gut microbiota, comprising Clostridia, Fusobacteriia, and Gammaproteobacteria. Molecular ecological network analysis described the complex inter-species interactions within the intestinal bacterial community, which in both groups was predominated by positive interactions. The dominant intestinal microbiota was found to be the major component of the ecological network and could play vital roles, for instance, as connectors, which have a major contribution in maintaining the stability of the bacterial community. The high-fat diet disturbed the intestinal microbiota homeostasis through the deterioration of the ecological network by reducing the average connectivity, negative interactions, and the number of connectors. Analysis of predicted functions (PICRUSt) showed that the high-fat diet significantly increased some potential functions of intestinal microbiota involved in lipid, amino acid, carbohydrate, and energy metabolism, in accordance with metabolic changes observed in terms of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, cholesterol, and glucose in the serum. These results suggested that the change in intestinal microbiota may contribute to the development of diet-induced fat deposition in eels.