title: Electron Shuttles Enhance Anaerobic Ammonium Oxidation Coupled to Iron(III) Reduction.
abstract: Anaerobic ammonium oxidation coupled to iron(III) reduction, termed Feammox, is a newly discovered nitrogen cycling process. However, little is known about the roles of electron shuttles in the Feammox reactions. In this study, two forms of Fe(III) (oxyhydr)oxide ferrihydrite (ex situ ferrihydrite and in situ ferrihydrite) were used in dissimilatory Fe(III) reduction (DIR) enrichments from paddy soil. Evidence for Feammox in DIR enrichments was demonstrated using the (15)N-isotope tracing technique. The extent and rate of both the (30)N2-(29)N2 and Fe(II) formation were enhanced when amended with electron shuttles (either 9,10-anthraquinone-2,6-disulfonate (AQDS) or biochar) and further simulated when these two shuttling compounds were combined. Although the Feammox-associated Fe(III) reduction accounted for only a minor proportion of total Fe(II) formation compared to DIR, it was estimated that the potentially Feammox-mediated N loss (0.13-0.48 mg N L(-1) day(-1)) was increased by 17-340% in the enrichments by the addition of electron shuttles. The addition of electron shuttles led to an increase in the abundance of unclassified Pelobacteraceae, Desulfovibrio, and denitrifiers but a decrease in Geobacter. Overall, we demonstrated a stimulatory effect of electron shuttles on Feammox that led to higher N loss, suggesting that electron shuttles might play a crucial role in Feammox-mediated N loss from soils.
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.|University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors: Guo-Wei
authors: GW
authors: Zhou
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.
authors: Xiao-Ru
authors: XR
authors: Yang
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.|University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors: Hu
authors: H
authors: Li
authors: Department of Surgery, University of Chicago , Chicago Illinois 60637, United States.|Biosciences Division, Argonne National Laboratory , 9700 South Cass Avenue Lemont, Illinois 60439, United States.
authors: Christopher W
authors: CW
authors: Marshall
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.|University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors: Bang-Xiao
authors: BX
authors: Zheng
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.|University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors: Yu
authors: Y
authors: Yan
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.
authors: Jian-Qiang
authors: JQ
authors: Su
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China.|State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, People's Republic of China.
authors: Yong-Guan
authors: YG
authors: Zhu
mesh_terms: D064751:Ammonium Compounds; D004583:Electrons; D005290:Ferric Compounds; D007501:Iron; D010084:Oxidation-Reduction
chemical_list: D064751:Ammonium Compounds; D005290:Ferric Compounds; D007501:Iron