Abstract
BackgroundThe blunt snout bream (Megalobrama amblycephala) is one of the most important commercial herbivorous fish in China, and dietary transition is an important event in blunt snout bream development. Gut microbiota has a vital role to host animal. However, little was known about the relationship among feeding habits transition, gut microbiota and digestive enzymes of gut content.ResultsIn this study, 186,328 high-quality reads from nine 16S rRNA libraries were obtained using the Illumina MiSeq PE300 platform. The valid sequences were classified into 388 Operational Taxonomic Units, and a total of 223 genera, belonging to 20 phyla, were identified. The clustering result of gut bacterial communities is consistently related to the clustering result of intestinal content compositions. Proteobacteria and Firmicutes constitute the ‘core’ gut microbiota of blunt snout bream. Cetobacterium and Rhizobium were identified as microbiological markers of gut microbiota at zooplankton-based diet stages and diet transition stages, respectively. Moreover, thirteen potential cellulose-degrading bacteria were detected in our study. The canonical redundancy analysis (RDA) revealed that the feeding habits strongly influenced the gut microbiota and the digestive enzyme activities of gut content, while the result of PICRUSt test suggests that the metabolic capacity of gut microbiota was affected by feeding habit.ConclusionsThis study provided a comprehensive survey of the gut microbiota in blunt snout bream during its dietary transition period for the first time and clearly showed that the gut microbiota was strongly affected by feeding habit. This work allows us to better understand the relationship among gut microbiota, nutrition metabolism and feeding habits in vertebrate. Further, our study provides a reference for future studies investigating the metabolic adaption of herbivorous fish to shift to a vegetarian diet during their life history.
Highlights
The blunt snout bream (Megalobrama amblycephala) is one of the most important commercial herbivorous fish in China, and dietary transition is an important event in blunt snout bream development
Classification of intestinal contents The intestinal contents were examined throughout the course of blunt snout bream development, and the prey organisms were classified into six categories: Rotifera, A. franciscana, Copepoda, Cladocera, L. minor and H. verticillata
This study presents a comprehensive survey of the gut microbiota in fish throughout the development of feeding habit, and it provides insight into the relationship among diet transition, digestive enzymes of gut content and intestinal microbiota for the first time
Summary
The blunt snout bream (Megalobrama amblycephala) is one of the most important commercial herbivorous fish in China, and dietary transition is an important event in blunt snout bream development. Gut microbiota has a vital role to host animal. The gut microbiota can be regarded as an additional ‘organ’ of the host animal with beneficial effects on metabolic capacity, energy utilization and storage, immune function and health. Some strains belonging to Clostridium, Methylobacterium, Enterobacter, Citrobacter, Bacillus and Pseudomonas isolated from the gastrointestinal tract of fish were identified as the potential cellulose-degrading bacteria [22,23,24,25]. Digestion of chitin is vital for the fish, which feed on zooplankton [25, 27]. Some strains belonging to Aeromonas, Vibrio, Plesiomonas, Acinetobacter, Flavobacterium and Bacillu, which were isolated from the digestive tract of Atlantic salmon, Dover sole, Japanese flounder, tilapia, respectively, were identified as the chitinase-producing bacteria [25, 28,29,30]
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