Toxicity of Cr(III) to Shewanella sp strain MR-4 during Cr(VI) reduction
Toxicity of Cr(III) to Shewanella sp strain MR-4 during Cr(VI) reduction
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DOI：
10.1021/es0622655
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发表时间：
2007-01-01
影响因子：
11.4
通讯作者：
Tebo, Bradley M.
中科院分区：
文献类型：
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作者：
Bencheikh-Latmani, Rizlan;Obraztsova, Anna;Tebo, Bradley M.
通过还原六价铬(作为铬酸盐离子，CrO42-)对铬的生物修复是基于这样的概念，即产物三价铬(Cr(III))比铬酸盐毒性更小。在这项研究中，我们发现，在pH 6-8的条件下，以Cr3+离子和/或羟基络合物(以下简称未络合的铬(III))的形式存在的可溶性铬(III)可以在相当大的浓度下被瞬时发现，并对希瓦氏菌(Shewanella sp.)产生有害影响。MR-4。然而，与有机配体络合或以氢氧化铬(3)(S)形式沉淀的铬(III)对细胞的影响很小或没有。类似地，在菌株MR-4还原铬(VI)的过程中，产物铬(III)的络合作用导致细胞存活率增加和铬(VI)还原活性延长。这些结果和定量逆转录聚合酶链式反应获得的基因表达数据表明，在铬(VI)还原过程中形成的或以非络合物种形式加入的铬(III)的毒性效应是由于干扰了细胞的基本活动，如DNA转录和/或复制。这项研究对铬(VI)污染场地的生物修复产生了重要的影响：希瓦纳氏菌对铬(VI)的还原。MR-4在形成过程中与铬(III)络合的化合物的存在增强和维持了MR-4，但反过来，铬(III)的络合排除了它的沉淀和固定化。
Bioremediation of chromium through the reduction of hexavalent chromium (as the chromate ion, CrO42-) is based on the notion that the product, trivalent chromium (Cr(III)), is less toxic than chromate. In this study, we show that soluble Cr(III), present at pH 6-8 as the Cr3+ ion and/or hydroxyl complexes (henceforth referred to as uncomplexed Cr(III)), can be found transiently in significant concentrations and has a deleterious effect on Shewanella sp. MR-4. However, Cr(III) complexed to an organic ligand or precipitated as Cr(OH)(3)(s) has little or no effect on cells. Similarly, during the reduction of Cr(VI) by strain MR-4, complexation of the product, Cr(III), results in increased cell survival and extended Cr(VI) reduction activity. These results and gene expression data obtained by qRT-PCR (quantitative reverse transcription-PCR) suggest that the observed toxic effect of Cr(III) formed during Cr(VI) reduction or added as an uncomplexed species is due to the interference with basic cell activities such as DNA transcription and/or replication. Important implications for the bioremediation of Cr(VI)-contaminated sites emerge from this study: Cr(VI) reduction by Shewanella sp. MR-4 is enhanced and sustained by the presence of compounds able to complex Cr(III) as it is being formed but, in turn, the complexation of Cr(III) precludes its precipitation and immobilization.