Dolomite Formation Mediated by Halophilic Archaeal Cells under Different Conditions and Carboxylated Microspheres

Dolomite is a widespread carbonate mineral in sedimentary rocks, and its formation mechanism have always attracted much attention. Most modern dolomite occurred in hypersaline environments and several microbial isolates from these environments have been reported to be able to induce dolomite formation as well. However the detailed mechanism of microbial induced dolomite remains largely unclear to date. In this study, a halophilic archaea, Natrinema sp. J7-1, was used to investigate what exactly played an important role in the microbial dolomite formation. Normal cells of Natrinema sp. J7-1 in post-log phase, inactive cells treated with carbonyl cyanide 3-cholorophenylhydrazine (CCCP, amitochondrial inhibitor), denatured cells treated by paraformaldehyde and glutaraldehyde, as well as carboxylated microspheres were used to induce dolomite formation. The mineral phases were identified by X-ray Diffraction(XRD), the morphologies of minerals, cells and microspheres were observed by Scanning Electron Microscope(SEM) and the functional groups on the surface of normal cells and denatured cells were analyzed by Fourier Transform Infrared Spectroscopy(FT-IR). Results showed that normal cells, inactive cells and carboxylated microspheres induced proto-dolomite formation successfully at the salinity of 280‰. In contrast, denatured cells were not capable of inducing the formation of dolomite, and the percentage of carboxyl groups on their surface decreased compared with normal cells. It can be concluded that carboxyl is one critical factor for microbially mediated dolomite formation, but respiration may count for little under our conditions.