Aerobically incubated bacterial biomass-promoted formation of disordered dolomite and implication for dolomite formation

Abstract

With the realization that the formation of low-temperature dolomite could involve the microbial activity, a new pathway to understand the origin and mechanism of dolomite is emerging. Although microbially mediated CaMg carbonates and dolomite occur in some aerobic and high-salinity conditions, little information about the exact role of aerobic microbes is available. Herein, a strain of moderately halophilic bacteria, Shewanella piezotolerans WP3, was selected to study the involvement of aerobically incubated bacterial biomass in the CaMg carbonate mineralization. Different biomass components were isolated from the bacterial cultures by a set of separation techniques, and used to mediate CaMg carbonate mineralization under a carbon dioxide diffused system. The experimental results showed that bacterial cells play a dominant role in the formation of disordered dolomite. And the mineralization of the disordered dolomite can be attributed to the bare cells and bound extracellular polymeric substances (bound EPS) isolated from the bacterial cells, most likely due to the promotion of high concentration and density of carboxyl and phosphoryl groups on the bacterial biomass (i.e., bare cells and bound EPS). Hence, it does imply that bacterial biomass, even without the active microbial activities, can also play an important role in the formation of dolomite. Current results can not only extend the insight into the biologically influenced mineralization of CaMg carbonates, but also shed light on the precipitation of disordered dolomite/dolomite in modern settings and geological records.