Characterization of the gut microbiota in the Anjak (Schizocypris altidorsalis), a native fish species of Iran

The antiquity, diversity and dietary variations among fish species present an exceptional opportunity for understanding the variety and nature of symbioses in vertebrate gut microbial communities. In this study for the first time the composition of the gut bacterial communities in the anjak was surveyed by 16S rRNA gene 454-pyrosequencing. Anjak (Schizocypris altidorsalis), is a native benthopelagic and commercially important fish species in Hamun Lake and Hirmand River system in Sistan basin, Iran. Thirteen 16S rRNA PCR libraries were generated, representing 13 samples of Anjak gut microbiota. After quality filtering, a total of 137 978 read pairs remained from the V3-V6 16S rRNA gene regions, each measuring 680 bp, and were assigned to bacterial OTUs at a minimum sequence homology of 97%, resulted in total 608 OTUs. The results provided evidence of the presence of a very diverse microbial community present in this fish. The majority of sequences belonged to members of the Firmicutes; however, members of the Proteobacteria, Tenericutes, Bacteroidetes and Cyanobacteria were also well represented in the anjak gut microbiota. The most abundant classes recorded in the samples were uncultured CK-1C4-19 class of Tenericutes, Flavobacteriia, -Proteobacteria, Erysipelotrichi, Synechococcophycideae, {gamma}-Proteobacteria, and Clostridia. The presence of many different types of bacteria in the anjak is not unexpected since it has been shown that eukaryotes with a detritivorous and planktivorous diet have a higher microbial diversity compared to omnivorous and herbivorous fish species. Many of these microbes might be of high physiological relevance for snow trout and may play key roles in the functioning of a healthy gut in this fish.