Effects of ecologically relevant concentrations of cadmium on locomotor activity and microbiota in zebrafish

Cadmium (Cd) is widely spread in the aquatic environment, and its impact on humans and the ecosystem is an important issue in public health. However, its effects on zebrafish microbiota are still poorly understood. In this study, the potential developmental neurotoxicity and microbiota dysbiosis of ecologically relevant concentrations of Cd (0, 1.25, 2.5 and 5 μg/L) was evaluated by waterborne exposure for 7 days. The data showed that exposure to 5 μg/L of Cd significantly decreased survival rates and impaired locomotor activities. Uptake of Cd was enhanced with the increase of the concentration and duration of exposure. High-throughput sequencing analysis revealed a significant change in the richness and diversity of the microbiota of Cd-treated zebrafish. At the phylum level, the abundance of Proteobacteria increased, while that Firmicutes was significantly decreased after exposure to 5 μg/L Cd. At the genus level, there were significant changes in the abundances of several bacteria involved in the regulation of neurodegenerative diseases (Pseudomonas, Ruminococcaceae, Blautia, Bacteroides, Lactobacillus, Lachnospiraceae, and Phascolarctobacterium) in the Cd-treatment groups, as compared to the control group. In addition, the mRNA expression profiles of bdnf and genes involved in serotonin signaling and metabolism were changed in the Cd exposure groups. Together, these data suggest that Cd could be harmful to zebrafish health by inducing the microbiota changes, and the microbiota could serve as a potential target to protect against the adverse effects of Cd toxicity.