Effect of CO2 leakages on autotrophic growth in the subsurface during geological sequestration

In recent years, the release of carbon dioxide into the atmosphere has been a growing concern. In order to mitigate this problem, technological options to help stabilize the CO2 concentrations have been studied by scientists all over the world. One of the more promising solutions, called geological sequestration, is comprised of pumping captured CO2 underground and storing it in deep saline aquifers. However, long-term storage CO2 raises concerns, the most prominent being the effect of the carbon dioxide if it were to escape. Batch reactors were set up to determine the effect of carbon dioxide on the aerobic bacterium Nitrosospria multiformis and the anaerobic archaeon Methanobacterium subterraneum. The N. multiformis was grown over a period of 5 days. Live and dead cells were enumerated using a BacLight kit and an epiflourescence microscope. The M. subterraneum was grown over a period of 6 days and enumerated using Flow-FISH (Flourescent In Situ Hybridization) with a MB1174 probe and DAPI. It was determined that both autotrophic growths were supported by carbon dioxide gas. The aerobic autotrophic bacterium N. multiformis had more growth when supplied with bicarbonate as a carbon source, but the CO2 had no inhibitory effects. The anaerobic archaeon M. Subterraneum growth was stimulated by the addition of CO2 gas. Optimization of this protocol would give more accurate results, but since little research has been conducted on the effect of geologic carbon sequestration on deep subsurface microbiology, this study laid down an important foundation for future research.