Investigating Nanoscale Electron Transfer Processes at the Cell-Mineral Interface in Cobalt-Doped Ferrihydrite Using Geobacter sulfurreducens: A Multi-Technique Approach
Investigating Nanoscale Electron Transfer Processes at the Cell-Mineral Interface in Cobalt-Doped Ferrihydrite Using Geobacter sulfurreducens: A Multi-Technique Approach
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DOI：
10.3389/feart.2022.799328
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发表时间：
2022-05
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通讯作者：
Dawn M. Buchanan;L. Newsome;Jonathan R. Lloyd;Majid Kazemian;B. Kaulich;Tohru Araki;H. Bagshaw;John Waters;Gerrit van der Laan;Alpha N’Diaye;V. Coker
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作者：
Dawn M. Buchanan;L. Newsome;Jonathan R. Lloyd;Majid Kazemian;B. Kaulich;Tohru Araki;H. Bagshaw;John Waters;Gerrit van der Laan;Alpha N’Diaye;V. Coker
钴是生活中必不可少的元素，由于其在可充电电池中的重要性，它在支持清洁能源方面发挥着至关重要的作用。Co通常与环境中的Fe相关联，但Co在富铁生物地球化学活跃环境中的命运却知之甚少。为了解决这个问题，使用同步加速器扫描x射线显微镜（SXM）研究了钴在微生物还原的Co-Fe(III)-羟基氧化物中的纳米级行为。SXM可以评估金属形态和有机化合物的空间变化，有助于阐明发生在细胞-矿物界面的电子转移过程，并告知钴在氧化还原层中的命运。G.硫还原剂用于还原合成的钴铁水合物，作为天然钴铁氧化物的类似物。粉末x射线衍射（XRD）、SXM和x射线磁圆二色性（XMCD）数据证实了磁铁矿[Fe(II)/Fe(III)3O4]的产生，其中x射线磁圆二色性（XMCD）数据与后者最吻合，表明含钴磁铁矿。宏观XAS技术表明，Co（III）发生了还原，纳米尺度上的互补SXM，加上成像，通过与外膜细胞色素的直接接触，在细胞-矿物界面上发现了局部的生物源Co（III）还原。在重新排序的钴-铁氧化物中，铁的形态没有明显的局部变化，在实验结束时，只有11%的Co和1.5%的Fe被溶解。固相保留，以及在纳米尺度上观察到的高度局部和优先的钴生物还原，与Co在氧化还原区的保留一致。这项工作提高了我们对复杂环境系统中Co命运的基本分子尺度理解，并支持生物共掺杂磁铁矿的开发，用于从药物输送系统到磁记录介质的工业应用。
Cobalt is an essential element for life and plays a crucial role in supporting the drive to clean energy, due to its importance in rechargeable batteries. Co is often associated with Fe in the environment, but the fate of Co in Fe-rich biogeochemically-active environments is poorly understood. To address this, synchrotron-based scanning X-ray microscopy (SXM) was used investigate the behaviour of cobalt at the nanoscale in Co-Fe(III)-oxyhydroxides undergoing microbial reduction. SXM can assess spatial changes in metal speciation and organic compounds helping to elucidate the electron transfer processes occurring at the cell-mineral interface and inform on the fate of cobalt in redox horizons. G. sulfurreducens was used to reduce synthetic Co-ferrihydrite as an analogue of natural cobalt-iron-oxides. Magnetite [Fe(II)/Fe(III)3O4] production was confirmed by powder X-ray diffraction (XRD), SXM and X-ray magnetic circular dichroism (XMCD) data, where best fits of the latter suggested Co-bearing magnetite. Macro-scale XAS techniques suggested Co(III) reduction occurred and complementary SXM at the nanoscale, coupled with imaging, found localised biogenic Co(III) reduction at the cell-mineral interface via direct contact with outer membrane cytochromes. No discernible localised changes in Fe speciation were detected in the reordered cobalt-iron-oxides that were formed and at the end point of the experiment only 11% Co and 1.5% Fe had been solubilised. The solid phase retention, alongside the highly localised and preferential cobalt bioreduction observed at the nanoscale is consistent with retention of Co in redox zones. This work improves our fundamental molecular-scale understanding of the fate of Co in complex environmental systems and supports the development of biogenic Co-doped magnetite for industrial applications from drug delivery systems to magnetic recording media.