Dynamics of the Gut Microbiome and Transcriptome in Korea Native Ricefish (Oryzias latipes) during Chronic Antibiotic Exposure

Antibiotics have been widely used to inhibit microbial growth and to control bacterial infection; however, they can trigger an imbalance in the gut flora of the host and dysregulate the host gene regulatory system when discharged into the aquatic environment. We investigated the effects of chronic exposure to a low concentration of erythromycin and ampicillin, focusing on gut microbiome and global gene expression profiles from Korea native ricefish (Oryzias latipes). The proportion of Proteobacteria (especially the opportunistic pathogen Aeromonas veronii) was significantly increased in the ricefish under the chronic exposure to erythromycin and ampicillin, whereas that of other bacterial phyla (i.e., Fusobacteria) decreased. In addition, the expression of genes involved in immune responses such as chemokines and immunocyte chemotaxis was significantly influenced in ricefish in the aquatic environment with antibiotics present. These results show that the internal microbial flora and the host gene expression are susceptible even at a low concentration of chronic antibiotics in the environment, supporting the importance of the appropriate use of antibiotic dose to maintain the sustainable and healthy aquaculture industry and water ecosystem.

Automated summary

Antibiotics, when present in aquatic environments at low concentrations, can disrupt the gut microbiome and host gene expression in fish, leading to an imbalance in microbial populations and impaired immune responses. This study found that chronic exposure to low concentrations of erythromycin and ampicillin significantly increased the proportion of opportunistic pathogens, such as Aeromonas veronii, in the fish, while decreasing the proportion of other bacterial phyla. The expression of immune response-related genes, such as chemokines and immunocyte chemotaxis, was also significantly affected in fish exposed to antibiotics in the aquatic environment.