Multi-omics association pattern between gut microbiota and host metabolism of a filter-feeding fish in situ exposed to microplastics

Microplastics (MPs) are widespread in water environments and can affect gut microbiota and host metabolism of fish, but whether changes in host metabolism under MPs are mediated by gut microbiota remains unclear. Here, silver carp, a filter-feeding fish with important ecological functions, was in-situ exposure to environmentally relevant MPs. Multi-omics analysis and fecal microbiota transplantation were used to reveal the metabolic responses of carp along gut-liver-muscle axis. After three months of in situ exposure to MPs, community structure of gut microbiota of carp was reshaped, and five dominate phyla were significantly changed, including increased Cyanobacteria, Chloroflexi and Planctomycetota but decreased Firmicutes and Fusobacteriota. Weighted gene co-expression network analysis was further performed between these phyla and liver transcription spectrum, showing that the hub gene module contained up-regulated hppD, maiA and plg and activated ubiquinone and other terpenoid-quinone biosynthesis and phenylalanine metabolism. By fecal microbiota transplantation, the key gene module associated with core microbiota phyla of carp was verified in germ-free zebrafish. Interestingly, up-regulated hppD, maiA and plg and enriched phenylalanine metabolism were also observed in this module. Subsequently, metabolome performed in carp liver also shared activated phenylalanine metabolism, including increased trans-cinnamic acid and L-tyrosine. Furthermore, high-associated mapping showed that the differentially expressed metabolites (gamma-aminobutyric acid, ornithine and L-serine) related to amino acid metabolism in carp muscle were significantly accompanied with increased L-tyrosine in its liver. Overall, MPs exposure could change gut microbiome of silver carp and alter host metabolism especially amino acid metabolism along the gut-liver-muscle axis.