title: Nitrate Stimulates Anaerobic Microbial Arsenite Oxidation in Paddy Soils.
abstract: Arsenic (As) bioavailability to rice plants is elevated in flooded paddy soils due to reductive mobilization of arsenite [As(III)]. However, some microorganisms are able to mediate anaerobic As(III) oxidation by coupling to nitrate reduction, thus attenuating As mobility. In this study, we investigated the impact of nitrate additions on As species dynamics in the porewater of four As-contaminated paddy soils. The effects of nitrate on microbial community structure and the abundance and diversity of the As(III) oxidase (aioA) genes were quantified using 16S rRNA sequencing, quantitative PCR, and aioA gene clone libraries. Nitrate additions greatly stimulated anaerobic oxidation of As(III) to As(V) and decreased total soluble As in the porewater in flooded paddy soils. Nitrate additions significantly enhanced the abundance of aioA genes and changed the microbial community structure by increasing the relative abundance of the operational taxonomic units (OTUs) from the genera Acidovorax and Azoarcus. The aioA gene sequences from the Acidovorax related OTU were also stimulated by nitrate. A bacterial strain (ST3) belonging to Acidovorax was isolated from nitrate-amended paddy soil. The strain was able to oxidize As(III) and Fe(II) under anoxic conditions using nitrate as the electron acceptor. Abiotic experiments showed that Fe(II), but not As(III), could be oxidized by nitrite. These results show that nitrate additions can stimulate As(III) oxidation in flooded paddy soils by enhancing the population of anaerobic As(III) oxidizers, offering a potential strategy to decrease As mobility in As-contaminated paddy soils.
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Shichen
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Wuxian
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Huang
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.
authors.forename: Zhu
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University , Nanjing 210095, China.|Sustainable Soils and Grassland Systems Department, Rothamsted Research , Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
authors.forename: Fang-Jie
authors.identifier: 0000-0002-0164-169X
authors.initials: FJ
authors.lastname: Zhao
mesh_terms: D018053:Arsenites / Q000378:metabolism*; D009566:Nitrates; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D018053:Arsenites; D009566:Nitrates; D012336:RNA, Ribosomal, 16S; D012987:Soil