Exposure to Oxy-Tetracycline Changes Gut Bacterial Community Composition in Rainbow Trout: A Preliminary Study

SIMPLE SUMMARY: The use of antibiotics is extensive in livestock and aquaculture, although various research work is being carried out across the globe for developing alternative technologies. However, the excessive use of antibiotics leads to bio-magnification due to their stability and persistence in the environment. We assessed the gut bacterial diversity of rainbow trout grown at aquacultures in Korea exposed to oxy-tetracycline for the restriction of infections. The study revealed the changes in taxonomic units upon antibiotic treatment and prediction-based functional characterization of the gut bacterial community, providing a general overview of the abundance of particular bacterial taxa. ABSTRACT: The extensive use of antibiotics is evident in most of the livestock and aquaculture management for inhibiting pathogen infection. Korean aquaculture depends on the usage of oxy-tetracycline for growing rainbow trout. Hence, this study was conducted to evaluate the changes in gut bacterial community profiles of rainbow trout exposed to oxy-tetracycline and predict the metabolic functioning of the bacterial community. The gut bacterial community composition of oxy-tetracycline treated fish was assessed by amplicon sequencing targeting the 16S rRNA gene of bacteria and comparing with the control group that did not receive any antibiotic. The principle coordinate analysis and non-metric multidimensional scaling analysis had shown two distinct clusters that implies the changes in community composition. In phyla level, the relative abundances of Tenericutes and Firmicutes were observed to be significantly higher in oxy-tetracycline treated fish compared to the control. Furthermore, the prediction based metabolic profiling revealed the processes that are affected due to the shift in community profiles. For example, metabolic functioning of membrane efflux system, amino acid metabolism and glycolysis were significantly higher in oxy-tetracycline treated fish compared to the control. This study describes alteration in gut bacterial community composition and potential metabolic profiles of the community that might be responsible for surviving in antibiotic rich environment.