Bacterially induced dolomite precipitation in anoxic culture experiments

To study the process of microbial-mediated dolomite formation, growth exper iments were carried out with selected bacterial cultures under anoxic envir onmental conditions simulating those found in Lagoa Vermelha, a hypersaline lagoon in Brazil where dolomite precipitation occurs. Specifically, we rep ort the isolation of a particular strain of sulfate-reducing bacteria, LVfo rm6, from Lagoa Vermelha sediment, which apparently promotes the formation of nonstoichiometric dolomite. Sulfate-reducing bacteria grown in a synthet ic liquid medium produced dolomite during 30 days incubation at 30 degreesC . The precipitates have morphologies similar to those observed in Lagoa Ver melha sediment. Our results demonstrate that sulfate-reducing bacteria can influence dolomite precipitation under controlled low-temperature, anoxic c onditions, and imply that anaerobic microorganisms can play an important ro le in carbonate sedimentation. They may have been particularly significant in Earth's earliest history when a more reducing atmosphere existed.