Antimony transformation and mobilization from stibnite by an antimonite oxidizing bacterium Bosea sp. AS-1

Soils and waters are heavily contaminated by antimony in Xikuangshan (XKS) mine area. It is widely accepted that oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment. Bosea sp. AS-1 is an antimonite-oxidizer isolated from the mine slag in Xikuangshan Sb mine. Whole genome sequencing revealed the presence of multiple sulfur-oxidizing genes, antimony (Sb) metabolism genes and carbon fixation genes in AS-1's genome. We therefore hypothesized that under oxic conditions, AS-1 could mediate the oxidation of sulfide and Sb(III) in stibnite (Sb₂S₃) and lead to the release of Sb. Indeed, strain AS-1 was discovered as an autotrophic Sb(III)-oxidizer. Antimony mobilization studies conducted with strain AS-1 showed significantly enhanced mobilization of Sb, and complete oxidation of released Sb and sulfur to Sb(V) and sulfate. In addition, AS-1 induced a faster release of Sb under heterotrophic condition, and new acicular minerals might form. These findings support the hypothesis that microorganisms play an important role in the mobilization and transformation of Sb in XKS mine area and may contribute to our further understanding of the Sb biogeochemical redox cycle in natural environment.