Variance analysis of bacterial community in the intestine of cultured spotted knifejaw (Oplegnathus punctatus) at different healthy levels and intervened with florfenicol

In order to evaluate the changes of the bacterial communities in the intestine of spotted knifejaw (Oplegnathus punctatus) at different healthy levels and intervened with florfenicol, and to find out the relationship with environmental factors, the Illumina HiSeq PE250 high-throughput technique was used to analyze the bacterial community diversity and structure of the fish intestine for healthy, sub-healthy, typical dark body disease (DBD) infected and oral florfenicol intervened individuals, as well as the culture water and pellet feed. The results showed that bacterial diversity in the culture water was higher than that of intestine and pellet feed. The dominant bacterial communities in intestine were Proteobacteria, Firmicutes and Tenericutes, at different health levels and with florfenicol intervention, and the proportions of corresponding operational taxonomic unit (OTU) number to all the OTU in the samples were above 85%. It could affect the ranking order of the top 20 dominant bacterial species in intestine when the DBD occurred, with the relative abundance of Vibrio in Proteobacteria increasing significantly. In addition, the DBD symptoms aggravated gradually, with the increase of Vibrio abundance. Feeding with florfenicol could reduce the Vibrio abundance from 60.33% to 1.29% in the intestine of diseased fish, and also change its structure of bacterial community to a greater degree, which proved that florfenicol was effective in treating DBD. It was also found that the culture water and pellet feed had a certain influence on intestine bacterial community, and the effect of the culture water was higher than the pellet feed. The present results would provide a reference basis and technical support for the health culture, disease control and microecological study in spotted knifejaw.