Exploring the microbial diversity of the distal intestinal lumen and mucosa of farmed rainbow trout Oncorhynchus mykiss (Walbaum) using next generation sequencing (NGS)

In this study, next generation sequencing (NGS) was used to survey the 16S rRNA ribotypes of the distal intestinal lumen and mucosal epithelium of farmed rainbow trout. This approach yielded a library consisting of 2979715 quality filtered paired sequences, assigned to genus level of taxonomy using the Ribosomal Database Project (RDP). A high level of diversity was observed in both regions. A total of 90 bacterial genera were identified in the lumen of all fish sampled, compared with 159 in the mucosa. The allochthonous microflora was dominated by sequences belonging to the Proteobacteria (mean sequence abundance 54.3%), in particular the Enterobacteriaceae, with Yersinia, Serratia, Hafnia and Obesumbacterium the most abundant genera. Fewer Proteobacteria (mean sequence abundance 37%) were present in the mucosa, and autochthonous communities consisted of a more even split among the bacterial classes, with increases in sequences assigned to members of the Proteobacteria (mean sequence abundance 18.4%) and Bacilli (mean sequence abundance 16.8%). The principal bacterial genera recorded in the mucosa were Cetobacterium, Yersinia, Ralstonia, Hafnia and Carnobacterium. The results of this study demonstrate that the luminal and mucosal bacterial communities may be different in their respective structures, and that the mucosal microflora of rainbow trout may be more diverse than previous research has suggested. This research also demonstrated a degree of conservation of bacterial genera between individual fish sampled, and is to the author's knowledge the first time the MiSeq((R)) NGS platform has been used to explore the rainbow trout intestinal microflora.