Catalytic Role of Anaerobic Bacteria in Dolomite Formation in Lake~Jibuhulangtu Nuur, Inner~Mongolia

Much attention has been attracted to understand the formation mechanism of dolomite, a long-standing problem in earth sciences. A~microbial dolomite model, proposed by geomicrobiologists, has been considered to provide new insights into this old enigma. Although authigenic dolomite is rare in modern marine sediments, the occurrence of dolomite can be found in some hypersaline environments (e.g., tidal flats and saline lakes). Therefore, these highly-evaporating environments are believed as nature laboratory for probing the role of microbe in dolomite formation. In this study, it reports a new discovery of modern dolomite in Lake Jibuhulangtu Nuur, a saline lake in Inner Mongolia. In order to address whether anaerobic microbes are involved in dolomite precipitation in this lake and whether sulfate ion has an impact on this reaction, precipitation experiments using microbial enrichment and pure culture were performed in lab. Our results show that both microbial consortium and strain JN-1 were capable of inducing dolomite precipitation. There were no ordering reflections in X-ray diffraction patterns, thus indicating that these biogenic dolomites were highly disordered. The observations by using scanning electron microscopy further show that the crystal morphology of biogenic dolomite developed during incubation period. In the early incubation stage, dolomite particles were sub-micron sized spherulites, however, they transformed into larger spheroids and dumbbell-shaped crystals. Furthermore, it seemed that sulfate had little effect on microbial dolomite formation. Our findings would be of significance for providing the basic data for the interaction between sulfate ions and dolomite formation, and improving our understanding of the formation mechanism of~dolomite