Bacterial diversity in gut of large yellow croaker Larimichthys crocea and black sea bream Sparus macrocephalus reared in an inshore net pen

Bacterial diversity in the foregut, midgut and hindgut of large yellow croaker Larimichthys crocea and black sea bream Sparus macrocephalus reared in an inshore net pen, formulated feed and seawater were analyzed with Illumina MiSeq high-throughput sequencing platforms. A total of 270 operational taxonomic units (OTUs) were identified from fish guts, formulated feed and seawater, which belonged to 17 phyla and 20 genera. Firmicutes and Proteobacteria dominated at the phylum level, while Bacillus, Lactococcus and Oceanobacillus dominated at the genus level, in fish gut. The similarity in bacterial community between the guts of two fish species was higher than that either between fish gut and formulated feed or between fish gut and seawater. This result indicates that bacterial communities in guts of large yellow croaker and black sea bream were independent on those in the formulated feed and seawater. The common OTUs between fish gut and formulated feed were more than that between fish gut and seawater, suggesting that the impact of the formulated feed on intestinal bacteria of large yellow croaker and black sea bream was greater relative to that of seawater in the net pen. Spatial heterogeneity in bacterial composition along the gut of large yellow croaker and black sea bream was also evaluated.