Objective: We studied the formation of carbonate minerals by bacteria to understand the mechanism of microbial mineralization.
Methods: Cultures of carbonate precipitation using Lagoa Vermelha medium with 6:1 molar ratio of Mg/Ca within 35 days were made under the mediation of Clostridium sp. (MH18 strain) isolated from soil. At the same time, aseptic experiments without the inoculation were done as the control. Mineral species were determined by X-ray diffraction, and the morphologies of precipitated carbonates were observed using optical microscopy and scanning electron microscopy.
Results: In the LV medium, MH18 strain mediated the formation of carbonate mineral, in which high-magnesium calcite was dominant. In the initial stage, the minerals had shapes with dumbbell-like morphology, and finally transformed to spheres. Only a small amount of precipitation appeared in the control, but X-ray diffraction patterns showed that these precipitations were amorphous substance.
Conclusions: MH18 strain could induce crystallization of carbonate.