Microbially mediated arsenate (As(V)) and Fe(III) reduction play important roles in arsenic (As) cycling in nature. Extracellular electron shuttles can impact microbial Fe(III) reduction, yet little is known about their effects on microbial As mobilization in soils. In this study, microcosm experiments consisting of an As-contaminated soil and microbial communities obtained from several pristine soils were conducted, and the effects of electron shuttles on As mobilization were determined. Anthraquinone-2,6-disulfonate (AQDS) and riboflavin (RF) were chosen as common exogenous and biogenic electron shuttles, respectively, and both compounds significantly enhanced reductive dissolution of As and Fe. Accumulation of Fe(II)-bearing minerals was also observed, which may lead to re-immobilization of As after prolonged incubation. Interestingly, Firmicutes-related bacteria became predominant in all microcosms, but their compositions at the lower taxonomic level were different in each microcosm. Putative respiratory As(V) reductase gene (arrA) analysis revealed that bacteria closely related to a Clostridia group, especially those including the genera Desulfitobacterium and Desulfosporosinus, might play significant roles in As mobilization. These results indicate that the natural soil microbial community can use electron shuttles for enhanced mobilization of As; the use of this type of system is potentially advantageous for bioremediation of As-contaminated soils.

中文翻译：

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细胞外电子穿梭对土壤微生物群落中砷动员活性的影响

微生物介导的砷酸盐（As（V））和Fe（III）的还原在自然界中的砷（As）循环中起重要作用。细胞外电子穿梭可以影响微生物中Fe（III）的还原，但对它们对土壤中微生物As迁移的影响知之甚少。在这项研究中，进行了由As污染土壤和从几种原始土壤中获得的微生物群落组成的微观实验，并确定了电子穿梭对As迁移的影响。分别选择2,6-二磺酸蒽醌（AQDS）和核黄素（RF）作为常见的外源和生物电子穿梭体，这两种化合物均显着增强了As和Fe的还原溶出。还观察到了含Fe（II）的矿物质的积累，长时间的温育后可能导致As的重新固定。有趣的是，与纤毛虫有关的细菌在所有微观世界中都占主导地位，但是在较低的分类学水平上，它们的组成在每个微观世界中都不同。推定的呼吸道As（V）还原酶基因（arrA）分析表明，与梭菌属密切相关的细菌，尤其是包括Desulfitobacterium和Desulfosporosinus在内的细菌，可能在As的动员中起重要作用。这些结果表明，天然土壤微生物群落可以利用电子穿梭来提高砷的迁移。这种类型的系统的使用对于砷污染土壤的生物修复具有潜在的优势。