Response of the gut microbiome of Megalobrama amblycephala to crowding stress.

Abstract Environmental factors, including drugs and diet, have been shown to affect the microbiome composition. However, whether physical factors affect the gut microbiome composition of fish and whether this change affects fish growth are unknown. The response of gut microorganisms to physical factors such as crowding was assessed by examining the gut microbiome and metabolome of fish from a high-density group and a low-density group. During the 90-day growth period, nine genera of gut microbes were significantly changed between the two groups. In addition, 32 metabolites were significantly changed between the two groups. The correlation analysis of differentially abundant gut microbes and metabolites allowed the identification of eight gut microbes, 13 metabolites and enrichment of seven metabolic pathways. Among the enriched pathways, the pentose phosphate pathway played potential role in the adaption of crowding stress and regulation of glucose metabolism. The response of the pentose phosphate pathway to crowding stress was further determined by evaluating key metabolites, biochemical changes, and the expression of a rate-controlling enzyme in this pathway. Our results provided new evidence that the gut microbiome might be involved in the response to crowding and consequently to the adaptation of fish to environmental stressors via the pentose phosphate pathway. Highlights • The growth of the fish was significantly affected by the stocking density. • Nine differential genera of gut microbes were identified involve in crowding. • 32 differential metabolites were identified involve in crowding. • Eight gut microbes correlated with 13 metabolites improving the crowding adaption. • The pentose phosphate pathway played a potential role in the crowding adaption. [ABSTRACT FROM AUTHOR]