Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens

Abstract

In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO 2 2+ , referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe 3+ ion. The results show that the production of mineralized solids {hydrogen−uranium mica [H 2 (UO 2 ) 2 (PO 4 ) 2 •8H 2 O]} via S. putrefaciens binding with UO 22+ is inhibited by DFO, which can both chelate preferentially UO 2 2+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe 3+ ion introduced, the strong specificity of DFO binding with Fe 3+ causes re-emergence of biomineralization of UO 2 2+ {bassetite [Fe(UO 2 ) 2 (PO 4 ) 2 •8(H 2 O)]} by S. putrefaciens, owing to competitive complexation between Fe 3+ and UO 2 2+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe 3+ and UO 2 2+ ions via these functional groups. The stability of the Fe 3+ -DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO 2 2+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.