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Instruments / Technical Area	Publication Details	Published	Actions
I08-Scanning X-ray Microscopy beamline (SXM)	Investigating nanoscale electron transfer processes at the cell-mineral interface in cobalt-doped ferrihydrite using Geobacter sulfurreducens: a multi-technique approach Dawn M. Buchanan , Laura Newsome , Jonathan R. Lloyd , Majid Kazemian , Burkhard Kaulich , Tohru Araki , Heath Bagshaw , John Waters , Gerrit Van Der Laan , Alpha N’diaye , Victoria S. Coker Frontiers In Earth Science 10 DOI: 10.3389/feart.2022.799328 Diamond Proposal Number(s): [17626] Open Access Show Abstract ▼ Abstract: 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.	May 2022
B18-Core EXAFS	Biomineralization of Cu2S nanoparticles by Geobacter sulfurreducens Richard L. Kimber , Heath Bagshaw , Kurt Smith , Dawn M. Buchanan , Victoria S. Coker , Jennifer S. Cavet , Jonathan R. Lloyd Applied And Environmental Microbiology DOI: 10.1128/AEM.00967-20 Diamond Proposal Number(s): [13705, 16136] Open Access Show Abstract ▼ Abstract: Biomineralization of Cu has been shown to control contaminant dynamics and transport in soils. However, very little is known about the role that subsurface microorganisms may play in the biogeochemical cycling of Cu. In this study, we investigate the bioreduction of Cu(II) by the subsurface metal-reducing bacterium, Geobacter sulfurreducens. Rapid removal of Cu from solution was observed in cell suspensions of G. sulfurreducens when supplied with Cu(II), while transmission electron microscopy (TEM) analyses showed the formation of electron dense nanoparticles associated with the cell surface. Energy-dispersive X-ray spectroscopy (EDX) point analysis and EDX spectrum image maps revealed the nanoparticles are rich in both Cu and S. This was confirmed by x-ray absorption near edge structure (XANES) and extended X-Ray absorption fine structure (EXAFS) analyses which identified the nanoparticles as Cu2S. Biomineralization of CuxS nanoparticles in soils has been reported to enhance the colloidal transport of a number of contaminants including Pb, Cd, and Hg. However, formation of these CuxS nanoparticles has only been observed under sulfate-reducing conditions and could not be repeated using isolates of implicated organisms. As G. sulfurreducens is unable to respire sulfate, and no reducible sulfur was supplied to the cells, these data suggest a novel mechanism for the biomineralization of Cu2S under anoxic conditions. The implications of these findings for the biogeochemical cycling of Cu and other metals as well as the green production of Cu catalysts are discussed.	Jul 2020

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