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首页> 外文期刊>Environmental Science & Technology >Toxicity of Cr(Ⅲ) to Shewanella sp. Strain MR-4 during Cr(Ⅵ) Reduction
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Toxicity of Cr(Ⅲ) to Shewanella sp. Strain MR-4 during Cr(Ⅵ) Reduction

机译：Cr（Ⅲ）对希瓦氏菌的毒性。 Cr（Ⅵ）还原过程中的MR-4菌株

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Bioremediation of chromium through the reduction of hexavalent chromium (as the chromate ion, CrO_4~(2-)) 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 Cr~(3+) 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 thatthe 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.
机译：通过还原六价铬（作为铬酸根离子CrO_4〜（2-））进行铬的生物修复是基于这样的观念，即三价铬（Cr（Ⅲ））的毒性小于铬酸根。在这项研究中，我们表明，在pH 6-8下，可以瞬时发现Cr（3+）离子和/或羟基络合物（以下称为未络合的Cr（Ⅲ））存在的可溶性Cr（Ⅲ）。浓度高，对希瓦氏菌具有有害作用。 MR-4。然而，与有机配体络合或以Cr（OH）_3（s）形式沉淀的Cr（Ⅲ）对细胞几乎没有影响。同样，在MR-4菌株还原Cr（Ⅵ）的过程中，产物Cr（Ⅲ）的络合增加了细胞的存活并延长了Cr（Ⅵ）的还原活性。这些结果和通过qRT-PCR（定量逆转录PCR）获得的基因表达数据表明，观察到的Cr（Ⅲ）还原过程中形成的或以未复合形式添加的Cr（Ⅲ）的毒性作用是由于干扰了基本细胞活性例如DNA转录和/或复制。这项研究对Cr（Ⅵ）污染位点的生物修复具有重要意义：Shewanella sp。还原Cr（Ⅵ）。通过形成能够络合Cr（Ⅲ）的化合物来增强和维持MR-4，但是，由于Cr（Ⅲ）的络合阻止了其沉淀和固定化。

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