Description
The anthropogenic use of platinum (Pt) has significantly altered its biogeochemical cycle over recent decades [1], leading to its increasing dispersion in the environment. Microorganisms, ubiquitous in ecosystems, strongly influence metal speciation. While some metals are essential for microbial metabolism, their transformations may also generate toxic forms that microorganisms mitigate through chelation or redox processes [2]. Although microbial interactions with Pt have been documented, the kinetic pathways and metabolic mechanisms driving Pt redox transformations, particularly at environmentally relevant concentrations, remain insufficiently constrained.
This study investigates the influence of the mesophilic bacterium Escherichia coli on Pt and sulfur (S) speciation. Cells were exposed to 100 µM Pt(IV) in nutritive medium, and Pt redox transformations were monitored using X-ray absorption spectroscopy (XAS) at the Pt L₃-edge. Results show that E. coli rapidly reduces Pt(IV) to Pt(II) within 1 hour, followed by further reduction to Pt(0) after 24 hours. Spectroscopic signatures indicate the involvement of S-bearing ligands during the reduction process. Complementary XAS analyses at the S K-edge, performed under the same exposure conditions, reveal an increase in reduced sulfur species (S(-II)) and a concomitant decrease in oxidized sulfur species (S(+V)), highlighting the central role of intracellular sulfur in Pt transformation and detoxification mechanisms.
These findings provide mechanistic insight into the coupling between bacterial sulfur metabolism and Pt redox kinetics, and contribute to a better understanding of microbial controls on Pt speciation and potential environmental mobility.
- Mitra, A.; Sen, I. S. Anthrobiogeochemical Platinum, Palladium and Rhodium Cycles of Earth: Emerging Environmental Contamination. Geochim. Cosmochim. Acta 2017, 216, 417–432. https://doi.org/10.1016/j.gca.2017.08.025.
- Gadd, G.M. (2013). Microbial Roles in Mineral Transformations and Metal Cycling in the Earth’s Critical Zone. In: Xu, J., Sparks, D. (eds) Molecular Environmental Soil Science. Progress in Soil Science. Springer, Dordrecht. https://doi-org.ezproxy.u-paris.fr/10.1007/978-94-007-4177-5_6
| Speaker information | PhD 3rd year |
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