Multi-Omics Analysis Reveals the Nitrogen Removal Mechanism Induced by Electron Flow during the Start-up of the Anammox-Centered Process

Abstract

Significant progress in understanding the key enzymes or species of anammox has been made; however, the nitrogen removal mechanism in complex coupling systems centered on anammox remains limited. In this study, by the combination of metagenomics−metatranscriptomics analyses, the nitrogen removal in the anammox-centered coupling system that entails partial denitrification (PD) and hydrolytic acidification (HA, A-PDHA) was elucidated to be the nitrogen transformation driven by the electron generation−transport−consumption process. The results showed that a total nitrogen (TN) removal efficiency of >98%, with a TN effluence of <1 mg/L and a TN removal contribution via anammox of >98%, was achieved after 59 days under famine operation and alkaline conditions during the start-up process. Further investigation confirmed that famine operation promoted the activity of genes responsible for electron generation in anammox, and increased the abundance or expression of genes related to electron consumption. Alkaline conditions enhanced the electron generation for PD by upregulating the activity of glyceraldehyde 3-phosphate dehydrogenase and strengthened electron transfer by increasing the gene encoding quinone pool. Altogether, these variations in the electron flow led to efficient nitrogen removal. These results improve our understanding of the nitrogen removal mechanism and application of the anammox-centered coupling systems in treating nitrogen wastewater.

Light-Driven Electron Uptake from Nonfermentative Organic Matter to Expedite Nitrogen Dissimilation by Chemolithotrophic Anammox Consortia

“…In this work, duplication in the molecular analysis was not set, as stated by Zhang et al (2022). 38 Other Analyses. NH 4 + , NO 2 − , NO 3 − , and VSS were measured according to standard methods.…”

“…The raw metagenomic and metatranscriptomic sequence reads were uploaded to the National Center for Biotechnology Information database with accession ID BioProject PRJNA902851. In this work, duplication in the molecular analysis was not set, as stated by Zhang et al (2022) …”

ZVI-Mediated High-Rate Nitrogen Removal from Fulvic Acid (FA)-Containing Wastewater by Anammox: Revealing the Genomic and Molecular Level Mechanisms

“…19 Moreover, the electron behaviors (generation, transport, and consumption) among ZVI, HS, and microorganisms are the most essential drive of this anammox system, and this series of reactions are encoded and controlled by key functional genes. 21 Recent advances in metagenomics allow for the characterization of functional genes and have been used to analyze the steps of N transformation driven by electron behaviors. For instance, Ma et al 22 used metagenomics to certify the multiple nitrogen transformations driven by electron behavior in a constructed wetland.…”

“…Zhang et al explain the mechanism of the electron flowmediated nitrogen removal in an anammox-centered coupling system. 21 Integrating the above techniques, the molecular shift pattern of HS molecular diversity caused by ZVI and microorganisms would be proposed. And further, the mechanism of ZVI mediating acceleration of the electron flow cycle under HS exposure, thereby enhancing the N removal, can be revealed from the perspective of electron behaviors.…”

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has paved the way for the appreciation of organic carbon profiles from the molecular level and was used to gain an increased understanding of organics heterogeneity in different environments . Moreover, the electron behaviors (generation, transport, and consumption) among ZVI, HS, and microorganisms are the most essential drive of this anammox system, and this series of reactions are encoded and controlled by key functional genes . Recent advances in metagenomics allow for the characterization of functional genes and have been used to analyze the steps of N transformation driven by electron behaviors.…”