Water Desalination and Reuse Center (WDRC), Biological and Environmental Science & Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.
BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, Twin Cities, St. Paul, MN, 55108, USA.
Nat Commun. 2020 Apr 28;11(1):2058. doi: 10.1038/s41467-020-16016-y.
Anaerobic ammonium oxidation (anammox) bacteria contribute significantly to the global nitrogen cycle and play a major role in sustainable wastewater treatment. Anammox bacteria convert ammonium (NH) to dinitrogen gas (N) using intracellular electron acceptors such as nitrite (NO) or nitric oxide (NO). However, it is still unknown whether anammox bacteria have extracellular electron transfer (EET) capability with transfer of electrons to insoluble extracellular electron acceptors. Here we show that freshwater and marine anammox bacteria couple the oxidation of NH with transfer of electrons to insoluble extracellular electron acceptors such as graphene oxide or electrodes in microbial electrolysis cells. N-labeling experiments revealed that NH was oxidized to N via hydroxylamine (NHOH) as intermediate, and comparative transcriptomics analysis revealed an alternative pathway for NH oxidation with electrode as electron acceptor. Complete NH oxidation to N without accumulation of NO and NO was achieved in EET-dependent anammox. These findings are promising in the context of implementing EET-dependent anammox process for energy-efficient treatment of nitrogen.
厌氧氨氧化（anammox）细菌对全球氮循环有重要贡献，在可持续废水处理中发挥着主要作用。anammox 细菌利用亚硝酸盐（NO）或一氧化氮（NO）等细胞内电子受体将铵（NH）转化为氮气（N）。然而，anammox 细菌是否具有将电子转移到不溶性细胞外电子受体的细胞外电子转移（EET）能力仍然未知。在这里，我们表明淡水和海洋 anammox 细菌将 NH 的氧化与电子转移到不溶性细胞外电子受体（如氧化石墨烯或微生物电解池中的电极）相耦合。N 标记实验表明，NH 通过羟胺（NHOH）作为中间产物氧化为 N，比较转录组学分析揭示了一种替代的 NH 氧化途径，其电子受体为电极。在依赖 EET 的 anammox 中，实现了 NH 到 N 的完全氧化，没有 NO 和 NO 的积累。这些发现有望在实施依赖 EET 的 anammox 工艺以实现节能处理氮的背景下得到应用。
