Mineral Influence on Microbial Survival During Carbon Sequestration

Geologic carbon sequestration involves the injection of supercritical carbon dioxide into deep saline aquifers. Some of the CO2 dissolves into the brines, perturbing water chemistry and water-rock interactions, and impacting microbial habitat and survival. In this study 3 model organisms were tested for their ability to survive high pressures of CO2 exposure in batch cultures: the gram-negative Shewanella oneidensis (SO) strain MR-1, the gram-positive Geobacillus stearothermophilus (GS), and the methanogenic archaeon Methanothermobacter thermoautitrophicus (MT). Results indicate that GS can survive the highest pressures of CO2 for the longest periods of time while SO is the most sensitive to CO2 toxicity. Survival was then evaluated for SO with various minerals and rocks representative of deep saline aquifers to determine if minerals enhanced survival. Cultures were exposed to 25 bar of CO2 for 2 to 8h and were plated for viable cell counts. Results show that biofilm formation on the mineral surface is important in protecting SO from the harmful effects of CO2 with quartz sandstones providing the best protection. The release of toxic metals like Al or As from minerals such as clays and feldspars, in contrast, may enhance microbial death under CO2 stress.