Microaerophilic Oxidation of Fe(II) Coupled with Simultaneous Carbon Fixation and As(III) Oxidation and Sequestration in Karstic Paddy Soil

Microaerophilic Fe(II)-oxidizing bacteria are often chemolithoautotrophs, and the Fe(III) (oxyhydr)oxides they form could immobilize arsenic (As). If such microbes active in karstic paddy soils, their activity would help increase soil organic carbon mitigate As contamination. We therefore used gel-stabilized gradient systems to cultivate microaerophilic from investigate capacity for Fe(II) oxidation, fixation, sequestration. Stable isotope probing demonstrated assimilation of inorganic at a maximum rate 8.02 mmol C m-2 d-1. Sequencing revealed that Bradyrhizobium, Cupriavidus, Hyphomicrobium, Kaistobacter, Mesorhizobium, Rhizobium, unclassified Phycisphaerales, Opitutaceas were fixing carbon. oxidation produced (oxyhydr)oxides, which can absorb and/or coprecipitate As. Adding As(III) decreased diversity functional involved relative abundance predicted fixation genes, amount fixed. Although was also lower presence As(III), over 90% sequestered after oxidation. The potential microbially mediated by arsenite oxidase gene (aioA), denoting autotrophic microbial community oxidize As(III). Thisstudy demonstrates coupled content soils bacteria, as well accelerate sequester it association with (oxyhydr)oxides.