Metagenomic Influential Insights in the Formation of Biogenic Iron Hydroxysulfate Precipitates by Ferrous Oxidative Microbial Consortia

The formation of iron hydroxysulfate precipitated minerals by microbial bioleaching is an undesired dominant process because it decreases the solubilization efficiency of targeted metals. To date, the microbial role in forming these precipitated minerals is unclear. Herein, we compared two microbial community diversity (consortia M1-18 and M8-15) with the distinct formation of secondary iron minerals. In the case of M1-18, a 16S rRNA metagenomic analysis revealed a higher microbial diversity and a prevalence of Ferrimicrobium and Acidimicrobiacea. This consortium also showed a slightly higher oxidation capacity and a remarkably higher particulate precipitate capacity of secondary minerals. In contrast, the consortium M8-15 showed lower diversity and poor precipitate capacity. XRD, EDS, and FE-SEM analysis of secondary iron minerals showed that the microbial consortia promote the mineralogical formation of the secondary iron precipitates in the form of schwertmannite, an early metastable phase that can be easily transformed to jarosite.