PROMOTED MOLYBDENUM AND IRON-CONTAINING MINERAL DISSOLUTIONS BY MICROBIALLY PRODUCED SIDEROPHORES

Siderophores play a crucial role in the dissolution of metal-bearing minerals to increase metal bioavailability for microbial uptake. Previous studies have extensively investigated mineral dissolutions by the model hydroxamate siderophore deferoxamine-B (DFOB), but the interactions between other various microbial siderophores and natural Mo-bearing minerals have not been explored. In this study, two distinct siderophores microbially produced tricatecholate protochelin and hydroxamate DFOB, were utilized to examine their effects on dissolutions of Mo-containing mineral molybdenite and Fe-bearing minerals (olivine, goethite, nontronite, and basalt) at the near-neutral pH. Concentrations of total dissolved metals (Mo or Fe) and solution siderophores were measured through batch experiments. The results demonstrated that both siderophores stimulated dissolutions of various iron minerals, and the surface-controlled dissolution processes are controlled by siderophore absorptions and metal-binding affinities. More importantly, protochelin enhanced molybdenite dissolution with the formation of molybdenum oxide (MoO₃) on the mineral surface. The dissolution of molybdenite increased with higher concentrations of protochelin, and a redox-driven dissolution mechanism was proposed for this process. Conversely, the addition of DFOB resulted in the depression of molybdenite dissolution. These findings shed light on the dissolution mechanisms of natural metal-bearing minerals promoted by siderophores. Specifically, it contributes to a deeper understanding of the biological molybdenum uptakes from solid mineral sources.