Metagenomics uncovers the effect of nitrogen-doped graphene on anammox consortia and microbial function.

[Display omitted] • N-G promoted anammox average nitrogen removal efficiency by 17.57%. • N-G increased anammox biomass from 18.10% to 28.30%. • N-G improved anammox microbial function in terms of "Metabolism". • N-G enriched the genes involved in nitrogen removal to varing degree. • N-G upregulated the genes controlling extracellular polymeric substance secretion. The effect of 50 mg/L nitrogen-doped graphene (N-G) on anammox microbial guild was studied by metagenomics in this paper. The continuous experiment results showed the average NRE improved by 17.57% with N-G addition. The metagenomic analysis revealed N-G significantly increased the relative abundance of dominant AnAOB (Candidatus Kuenenia) from 18.10% to 28.30%. And the FISH assay further manifested N-G promoted the growth of AnAOB biomass. Meanwhile, metagenomics indicated that N-G enriched the abundance of genes (Hzs , Hdh , NosZ , NorB , NirK , NirS and NrfA) involved in nitrogen metabolism to varying degrees. Furthermore, N-G not only improved the microbial functionality in terms of "Metabolism", but markedly upregulated the abundance of c-di-GMP synthesized genes and genes related to quinolone signal molecule, which contributed to more EPS content and better sludge settleability. In brief, this study provided a novel perspective for anammox biomass enrichment, which may be valuable for practical engineering applications of anammox. [ABSTRACT FROM AUTHOR]