Microbial reduction of actinides: classification, speciation dependency and environmental applications

• Applicant: Professor Dr. Thorsten Stumpf
• Subject Area: Microbial Ecology and Applied Microbiology ; Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569087738

MIRACLE is an interdisciplinary French-German project combining molecular microbiology, biogeochemistry, geochemistry and analytical chemistry with basic spectroscopic techniques to systematically categorize microbial uranium (U) reduction processes. We will examine initial U(VI) speciation, the biogenic U(IV) products formed, and the role of U(V) as a key intermediate. We will use advanced spectroscopic and microscopic techniques to elucidate these processes in 3 microbial genera: Shewanella, Desulfosporosinus, and Anaeromyxobacter. Various U(VI) complexes, including wellcharacterized complexes formed after complexation with extraction products from wetlands, will be screened to investigate the speciation dependency of microbial U(VI) reduction and complexation strength and kinetic of dissociation. State-of-the-art high-energy resolution fluorescence-detected X-ray near-edge structure (HERFD-XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy will provide insights into the U reduction products formed and the presence of U(V) during this process, as the occurrence and stability of this oxidation state are still poorly understood. Additionally, high-energy resolution fluorescence detected X-ray fluorescence (HERFD-XRF) mapping will be applied for the first time on biogenic samples to elucidate the spatial distribution of the different U oxidation states in the biomass. Proteomic and/or transcriptomic analyses will be also conducted to gain a comprehensive understanding of the molecular mechanisms underlying U(VI) reduction. This project will fill existing gaps in the research on microbial U(VI) reduction by providing a comprehensive classification of reduction processes. Consequently, this research will not only aid in developing new bioremediation strategies but also contribute to a thorough safety analysis for the deep geological disposal of radioactive waste, ultimately helping to protect groundwater and drinking water from U contamination.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partners: Dr. Virginie Chapon; Dr. Gilles Montavon