219 / 2025-04-15 11:14:26

Synergistic microbial interactions promote stibnite dissolution and antimony oxidation

Synergistic microbial,Stibnite dissolution,Antimony oxidation,Extracellular polymeric substances

Theme 5: Life-Mineral Interaction and Evolutions > Session 5d: Microbe-mineral Interaction and Its Environmental Impact

Antimony (Sb) is a toxic metalloid widely distributed in mining-impacted environments, where its mobility and speciation are strongly influenced by microbial activity. In particular, microbe-mineral interactions at the solid-liquid interface play a critical role in controlling Sb transformation and release. However, the mechanisms by which microbial cooperation mediate stibnite (Sb₂S₃) weathering and Sb(III) oxidation remain poorly understood. In this study, we constructed a synthetic two-strain microbial system composed of Shinella sp. (capable of Sb(III) oxidation) and Brevundimonas sp. (incapable of Sb(III) oxidation), to investigate the synergistic effects of co-cultivation on stibnite dissolution and Sb transformation. Experimental results showed that co-cultivation of strains Shinella sp. and Brevundimonas sp. significantly enhanced both stibnite dissolution and Sb(III) oxidation, compared to monocultures. Quantitative PCR analysis revealed that Brevundimonas sp.’s abundance increased significantly in co-culture, implying that its growth was promoted by Shinella sp. Scanning electron microscopy (SEM) showed that co-cultures produced more extracellular polymeric substances (EPS), which formed aggregates on the olid-liquid interface, whereas strain Shinella sp. remained mostly dispersed in monoculture. Confocal laser scanning microscopy (CLSM) further revealed that polysaccharide signals were present in Brevundimonas sp. and the co-culture, but absent in Shinella sp., suggesting that Brevundimonas sp. was the primary source of polysaccharide-rich EPS. XPS results revealed the highest proportion of Sb(V) in the co-culture (18.22%), alongside the most extensive sulfur species transformation. Specifically, the co-culture showed increased conversion of sulfide (S²⁻) to disulfide (S₂²⁻), with S₂²⁻ reaching 30.57%, substantially higher than in abiotic (20.95%) or monoculture groups. To directly evaluate the role of EPS, purified EPS from strain Brevundimonas sp. was added to strain Shinella sp. cultures during leaching experiments. The addition enhanced Shinella sp.’s adhesion to mineral surfaces and promoted Sb(III) oxidation. Fourier Transform Infrared Spectroscopy (FTIR) analysis of the co-culture EPS revealed distinct peaks at 2964, 2933, 1239, and 1079 cm⁻¹, corresponding to C–H, C–O/C–N, and P–O bonds. Further quantitative analysis showed that the co-culture produced more extracellular polysaccharides and proteins than either monoculture. Three-Dimensional Excitation-Emission Matrix Fluorescence Spectroscopy (3D-EEM) revealed strong signals in the Ex/Em = 300-450/400-550 nm range, corresponding to humic-like substances. Among all groups, the co-culture exhibited the highest fluorescence intensity. Collectively, these results demonstrate that EPS-mediated microbial synergy significantly promotes stibnite weathering and Sb oxidation. Brevundimonas sp.-derived EPS facilitates the adhesion and oxidative activity of Shinella sp., while also altering sulfur speciation at the mineral surface. This study provides mechanistic insights into microbe-mineral interactions and offers theoretical support for microbial strategies in remediating Sb-contaminated environments.