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Effects of the Anaerobic Respiration of Shewanella oneidensis MR-1 on the Stability of Extracellular U(VI) Nanofibers

机译:沙瓦氏假单胞菌MR-1厌氧呼吸对细胞外U(VI)纳米纤维稳定性的影响

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摘要

Uranium (VI) is considered to be one of the most widely dispersed and problematic environmental contaminants, due in large part to its high solubility and great mobility in natural aquatic systems. We previously reported that under anaerobic conditions, Shewanella oneidensis MR-1 grown in medium containing uranyl acetate rapidly accumulated long, extracellular, ultrafine U(VI) nanofibers composed of polycrystalline chains of discrete meta-schoepite (UO3·2H2O) nanocrystallites. Wild-type MR-1 finally transformed the uranium (VI) nanofibers to uranium (IV) nanoparticles via further reduction. In order to investigate the influence of the respiratory chain in the uranium transformation process, a series of mutant strains lacking a periplasmic cytochrome MtrA, outer membrane (OM) cytochrome MtrC and OmcA, a tetraheme cytochrome CymA anchored to the cytoplasmic membrane, and a trans-OM protein MtrB, were tested in this study. Although all the mutants produced U(VI) nanofibers like the wild type, the transformation rates from U(VI) nanofibers to U(IV) nanoparticles varied; in particular, the mutant with deletion in tetraheme cytochrome CymA stably maintained the uranium (VI) nanofibers, suggesting that the respiratory chain of S. oneidensis MR-1 is probably involved in the stability of extracellular U(VI) nanofibers, which might be easily treated via the physical processes of filtration or flocculation for the remediation of uranium contamination in sediments and aquifers, as well as the recovery of uranium in manufacturing processes.
机译:铀(VI)被认为是分布最广,问题最严重的环境污染物之一,这在很大程度上归因于其高溶解度和在天然水生系统中的高迁移率。我们以前曾报道过,在厌氧条件下,在含乙酸铀酰的培养基中生长的矮小希瓦氏菌MR-1迅速积聚了长的,胞外的,超细的U(VI)纳米纤维,该纤维由不连续的斜长晶石(UO 3 ·2H2O)纳米晶体。野生型MR-1最终通过进一步还原将铀(VI)纳米纤维转变为铀(IV)纳米颗粒。为了研究呼吸链在铀转化过程中的影响,一系列突变菌株缺少周质细胞色素MtrA,外膜(OM)细胞色素MtrC和OmcA,锚定在细胞质膜上的四血红素细胞色素CymA和反式-OM蛋白MtrB,在这项研究中进行了测试。尽管所有突变体都像野生型一样产生了U(VI)纳米纤维,但是从U(VI)纳米纤维到U(IV)纳米颗粒的转化率却有所不同。特别是,在四血红素细胞色素CymA中缺失的突变体稳定地维持了铀(VI)纳米纤维,这表明沙门氏菌MR-1的呼吸链可能参与了细胞外U(VI)纳米纤维的稳定性,这可能很容易通过过滤或絮凝的物理过程进行处理,以补救沉积物和含水层中的铀污染,以及在生产过程中回收铀。

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