<i>Arthrobacter Sp</i>. Strain MF-2 Induces High-Mg Calcite Formation: Mechanism and Implications for Carbon Fixation

Abstract

To better understand the mechanism of formation of carbonate minerals by microbes, culture experiments with Arthrobacter sp. strain MF-2 were carried out using M2 medium without carbonate ions for 50 days. A series of sterile control experiments without bacteria were run simultaneously. During the incubation, cell density, the quantity of precipitate, the extracellular polysaccharide (EPS) content, the activity of carbonic anhydrase (CA), the low molecular weight organic acid concentration, the pH, the electrical conductivity, and the Ca2+ and Mg2+ concentrations of the medium were determined. The morphologies of the precipitated carbonates were observed using scanning electron microscopy, and their mineral species were determined by X-ray diffraction. The results demonstrated that the quantity of precipitate in the biotic experiments increased gradually with the incubation time; precipitate was not obtained in the abiotic experiments. The average precipitation rate correlated positively with the cell density and the EPS content, with r = 0.64 and 0.61, respectively. This suggests that bacterial cells and EPS effected carbonate precipitation. Carbonate ion incorporation into minerals results from carbon dioxide hydration, promoted by microbial secretion of CA by bacteria. These findings contribute to the ongoing search for feasible mechanisms for the sequestration of carbon dioxide in the subsurface, in this case mediated by microorganisms.