Analysis of bacterial community structure in culture water of recirculating aquaculture systems of Fugu bimaculatus

16S rRNA high-throughput generation sequencing technology was used to study the bacterial community characteristics of culture water of recirculating aquaculture system(RAS)for Fugu bimaculatus.In order to elucidate the relationship between bacterial community and the occurrence of bacterial disease,the difference of bacterial community structure of sick and healthy culture water was compared.The results showed that the composition of bacterial communities in sick and healthy culture water was highly similar,there was no significant difference in the Alpha-diversity of bacterial community.The dominant phylums of the bacterial in culture water of RAS were Proteobacteria and Bacteroidetes,while the dominant classes of bacteria were Gammaproteobacteria,Flavobacteriia and Alphaproteobacteria.The dominant orders of bacteria were Flavobacteriales,Thiotrichales,Rhodobacterales,Alteromonadales and Vibrionales,while the dominant family of bacteria were Flavobacteriaceae,Thiotrichaceae,Rhodobacteraceae,Vibrionaceae and Pseudoalteromonadaceae.However,the abundance ratio of bacterial communities at the same classification level was significantly different in sick and healthy culture water.The core micro-organisms(genus) was obviously different between sick and healthy culture water.The core micro-organisms in the healthy culture waters was dominated by Polariclaer;while the core micro-organisms in the sick culture waters were Photobacterium and Vibrio of Vibrionales.The Photobacterium and Vibrio were reported as pathogenic bacteria or conditional pathogenic bacteria.The occurrence of ulceration in F.bimaculatus was associated with a high proportion of Vibrio abundance in bacterial communities in cultured waters.The results were of great significance for monitoring,early warning,diagnosis and management control of bacterial diseases in recirculating aquaculture of F.bimaculatus.