1. Nitrate Stimulates Anaerobic Microbial Arsenite Oxidation in Paddy Soils
- Author
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Zhu Tang, Shi-Chen Zhao, Jun Zhang, Fang-Jie Zhao, Wuxian Zhou, Ke Huang, and Yan Xu
- Subjects
0301 basic medicine ,Arsenites ,Population ,010501 environmental sciences ,01 natural sciences ,Soil ,03 medical and health sciences ,chemistry.chemical_compound ,Nitrate ,RNA, Ribosomal, 16S ,Botany ,Environmental Chemistry ,Nitrite ,education ,Soil Microbiology ,0105 earth and related environmental sciences ,Arsenite ,education.field_of_study ,Nitrates ,biology ,Acidovorax ,General Chemistry ,biology.organism_classification ,Anoxic waters ,030104 developmental biology ,chemistry ,Microbial population biology ,Oxidation-Reduction ,Soil microbiology - 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.
- Published
- 2017