Single-Cell Imaging and Spectroscopic Analyses of Cr(VI) Reduction on the Surface of Bacterial Cells

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• 作者：Yuanmin Wang ; Papatya C. Sevinc ; Sara M. Belchik ; Jim Fredrickson ; Liang Shi ; H. Peter Lu
• 刊名：Langmuir
• 出版年：2013
• 出版时间：January 22, 2013
• 年：2013
• 卷：29
• 期：3
• 页码：950-956
• 全文大小：389K
• 年卷期：v.29,no.3(January 22, 2013)
• ISSN：1520-5827

文摘

We investigate the single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process, using Raman spectroscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Our experiments indicate that the toxic, highly soluble Cr(VI) can be efficiently reduced to less toxic, nonsoluble Cr₂O₃ nanoparticles by MR-1. Cr₂O₃ is observed to emerge as nanoparticles adsorbed on the cell surface and its chemical nature is identified by EDX imaging and Raman spectroscopy. Co-localization of Cr₂O₃ and cytochromes by EDX imaging and Raman spectroscopy suggests a terminal reductase role for MR-1 surface-exposed cytochromes MtrC and OmcA. Our experiments revealed that the cooperation of surface proteins OmcA and MtrC makes the reduction reaction most efficient, and the sequence of the reducing reactivity of MR-1 is wild type > single mutant 螖mtrC or mutant 螖omcA > double mutant (螖omcA鈥撐?i>mtrC). Moreover, our results also suggest that direct microbial Cr(VI) reduction and Fe(II) (hematite)-mediated Cr(VI) reduction mechanisms may coexist in the reduction processes.