Barite crusts from a brine pool in the Gulf of Mexico and the role of sulfur oxidizing bacteria in the precipitation of barite (BaSO4)

Abstract

Barite (BaSO4) is found in certain benthic marine settings, sometimes in proximity to microbial mat communities. However, barite precipitation is typically thought to form from a mixing of sulfate and barium rich fluids. Barite mineral crusts collected from a brine pool in the Gulf of Mexico contain filamentous mineral structures of grossly similar morphology to filamentous surrounding sulfur-oxidizing Beggiatoa mats. Molecular analyses of DNA preserved in the Gulf of Mexico barite crusts suggest that microbial sulfur-oxidation could play a role in the formation of these authigenic precipitates. Laboratory experiments using several strains of benthic marine bacteria show that sulfide-oxidizing bacteria have the capability to mediate barite precipitation via the oxidation of reduced sulfur compounds to sulfate. The results of this study suggest that sulfide-oxidizing bacteria may play a role in the precipitation of certain marine barite deposits, and expands the potential role of bacteria in marine barite formation to include their potential to generate sulfate under sulfate-limited conditions, such as some brine fluids.