Animal gut microbiome mediates the effects of antibiotic pollution on an artificial freshwater system.

The antibiotic pollution has become an emerging environmental problem worldwide, but the ecological outcomes remain to be elucidated, especially very little is known about the interactions between antibiotics and different ecological elements. In this study, the long-term influences of three representative antibiotics, i.e., tetracycline, erythromycin, and sulfamethoxazole, were investigated focusing on a simplified artificial freshwater system composed of amphibian tadpoles, gut and environmental bacterial and fungi communities, and water parameters. Results demonstrated that antibiotic exposure reduced tadpole's fitness with increased mortality and physiological abnormality, and altered the water quality, particularly the nitrogen homeostasis. Sequential analyses at organism, symbiont, and systematic levels revealed that antibiotics disrupted tadpole metabolome (e.g., tetrahydrobiopterin metabolism) directly by off-target effects. Antibiotics also reshaped the tadpole gut bacterial and fungi diversity and composition, which partly accounted for the tadpole's health condition. Moreover, changes of tadpole gut microbiome (i.e., Cyanobacteria and Basidiomycota OTUs) partly explained the variations of water parameters. In contrast, environmental microbiota and metagenome stayed relatively stable, and didn't contribute to the environmental variations. These results highlighted the pivotal role of gut microbiome in mediating the effects of antibiotics on the host and the environment, which would extend our understanding on the ecological outcomes caused by antibiotic pollution.