Community composition, diversity, and metabolism of intestinal microbiota in cultivated European eel (Anguilla anguilla)

The intestinal tract, which harbours tremendous numbers of bacteria, plays a pivotal role in the digestion and absorption of nutrients. Here, high-throughput sequencing technology was used to determine the community composition and complexity of the intestinal microbiota in cultivated European eels during three stages of their lifecycle, after which the metabolic potentials of their intestinal microbial communities were assessed. The results demonstrated that European eel intestinal microbiota were dominated by bacteria in the phyla of Proteobacteria, followed by Fusobacteria and Firmicutes or Bacteroidetes. Statistical analyses revealed that the three cultured European eel life stages (elver, yellow eel and silver eel) shared a core microbiota dominated by Aeromonas. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) predictions of metagenome function revealed that the European eel intestinal microbiota might play significant roles in host nutrient metabolism. Biolog AN MicroPlateTM analysis and extracellular enzyme assays of isolated intestinal bacteria showed that the intestinal microbiota have a marked advantage in the metabolism of carbohydrates and nucleotides, followed by the metabolism of carboxylic and amino acids. Understanding the ecology and functions of the intestinal microbiota during different developmental stages will help us to improve the effects of fish-based bacteria on the composition and metabolic capacity of nutrients in European eels.