Oxidation state of chromium associated with cell surfaces of Shewanella oneidensis during chromate reduction
Oxidation state of chromium associated with cell surfaces of Shewanella oneidensis during chromate reduction
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DOI：
10.1016/s0169-4332(02)00550-0
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发表时间：
2002-12-30
影响因子：
6.7
通讯作者：
Little, BJ
中科院分区：
文献类型：
--
作者：
Neal, AL;Lowe, K;Little, BJ
利用电子能量损失谱（EELS）和x射线光电子能谱（XPS），我们证明了在有氧和厌氧培养中，希瓦氏菌细胞都能够还原铬酸盐。cr2p（3/2）芯光电子能谱在细胞表面未发现CC（VI）和Cr(V)物质。从厌氧培养基中回收的细胞表面的铬含量高于好氧培养基。采用Cr（III）和Cr（IV）的多重分裂模型来确定每种离子对从不同细胞处理中收集的Cr 2P（3/2）光峰的贡献。虽然在所有情况下，Cr（III）都是与细胞表面相关的主要离子，但在厌氧生长的细胞中，Cr（IV）的贡献很大。当细胞需氧生长时，Cr（IV）的贡献要小得多。此外，当厌氧培养的细胞暴露于氧气中时，很少发生Cr沉淀的再氧化，沉淀再次被确定为Cr（III）和Cr（IV）的混合物。观察到铬和磷的数量与各种处理产生的细胞表面相关，表明沉淀包括Cr(III)-磷酸盐。Cr（IV）在再氧化后仍然与沉淀相关联，这一事实表明，在厌氧条件下，中间离子具有足够的稳定性，可以与沉淀基质结合，从而获得一定程度的抗氧化保护。(C) 2002年Elsevier Science B.V.出版
Employing electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS), we demonstrate that in both aerobic and anaerobic culture Shewanella oneidensis cells are capable of chromate reduction. No CC(VI) or Cr(V) species were identified at the cell surfaces in Cr 2P(3/2) core photoelectron spectra. More chromium was associated with cell surfaces recovered from anaerobic medium than aerobic. Multiplet-splitting models derived for Cr(III) and Cr(IV) were employed to determine contributions from each ion to Cr 2P(3/2) photopeaks collected from the various cell treatments. whilst in all cases Cr(III) was the major ion associated with cell surfaces, a significant contribution was identified due to Cr(IV) in anaerobically grown cells. The Cr(IV) contribution was far less when cells were grown aerobically. Moreover, when anaerobically grown cells were exposed to oxygen very little re-oxidation of Cr-precipitates occurred, the precipitates were again identified as a mixture of Cr(III) and Cr(IV). A positive relationship was observed between amounts of chromium and phosphorous associated with cell surfaces resulting from the various treatments, suggesting the precipitates included Cr(III)-phosphate. The fact that Cr(IV) remained associated with precipitates following re-oxidation suggests that under anaerobic conditions the intermediate ion is afforded sufficient stability to be incorporated within the precipitate matrix and thus conferred a degree of protection from oxidation. (C) 2002 Published by Elsevier Science B.V.