Goldfish growth inhibition and gut microbial community shift induced by exposure to carboxylated multi-walled carbon nanotubes.

Exposure to carbon nanotubes may hinder animal growth. Gut microbiota is closely associated with lipid metabolism in animals, yet its role in the growth impairment of fish induced by carbon nanotubes remains unclear. In this study, juvenile goldfish (Carassius auratus) was exposed to 0-1000 μg/L carboxylated multi-walled carbon nanotubes (MWCNT-COOH) for four weeks to find the correlations between gut microbial community and the induced toxicities. MWCNT-COOH was found to induce histopathological and oxidative damages to liver. The weight of fish body and liver decreased after the MWCNT-COOH exposure at any dose after 14 days (p < 0.05). Pyrosequencing of 16S rRNA gene amplicon showed the MWCNT-COOH exposure greatly disturbed gut microbial community of the fish by increasing the relative abundance of Bacteroidetes phylum and Bacteroides genus and inhibiting Proteobacteria and Firmicutes phyla and Vibrio genus. Correlation and network analyses consistently indicated that the liver weight and body weight changes were positively correlated with the alterations of Firmicutes/Bacteroidetes ratio and negatively correlated with the increase of Bacteroidetes and Bacteroides abundance. Our results suggested that MWCNT-COOH inhibited fish growth by modulating the intestinal microbiota and subsequently disturbing the lipid metabolism.