Humic substances as electron acceptors for anaerobic oxidation of methane driven by ANME-2d. (1st November 2019)

• Record Type: Journal Article
• Authors: Bai, Ya-Nan; Wang, Xiu-Ning; Wu, Jun; Lu, Yong-Ze; Fu, Liang; Zhang, Fang; Lau, Tai-Chu; Zeng, Raymond J.
• Is Part Of: Water research. Volume 164(2019)
• Publication Date: 2019-11-01
• Subjects: Humics -- Methane -- Anaerobic oxidation of methane (AOM) -- Electron acceptors -- ANME-2d; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2019.114935
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Humic substances (humics) are ubiquitous in terrestrial and aquatic environments where they can serve as electron acceptors for anaerobic oxidation of organic compounds. Methane is a powerful greenhouse gas, as well as the least reactive organic molecule. Anaerobic oxidation of methane (AOM) coupled to microbial reduction of various electron acceptors plays a crucial role in mitigating methane emissions. Here, we reported that humics could serve as terminal electron acceptors for AOM using enriched nitrate-reducing AOM microorganisms. AOM coupled to the reduction of humics was demonstrated based on the production of 13 C-labelled carbon dioxide, and AOM activity was evaluated with different methane partial pressures and electron acceptor concentrations. After three-cycle reduction, both AOM activity and copy numbers of the archaea 16S rRNA and mcr A genes were the highest when anthraquinone-2, 6-disulfonic acid and anthraquinone-2-sulfonic acid were electron acceptors. The high-throughput sequencing results suggested that ANME-2d were the dominant methane oxidation archaea after humics reduction, although the partner bacteria NC10 trended downward, other reported humics reduction bacteria ( Geobactor and Anammox) appeared. The potential electron transfer models from ANME-2d to humics were proposed. These results enable a better understanding of available electron acceptors for AOM in natural environments and broaden our insight into the significant role of ANME-2d. Graphical abstract: Image 1 Highlights: Humics can serve as electron acceptors for anaerobic oxidation of methane (AOM). AOM activity is the highest with AQDS and AQS after three-cycle reduction. ANME-2d are the dominant methane oxidation archaea throughout the experiments. Other reported humics reduction bacteria appear after three-cycle reduction. The distinguishing electron transfer models between nitrate and humics reduction are proposed.