Genomic insights into growth and survival of supercritical-CO2 tolerant bacterium MIT0214 under conditions associated with geologic carbon dioxide sequestration

Carbon capture and storage (CCS) of CO2 has the potential to significantly reduce the emissions of greenhouse gasses associated with fossil fuel combustion. The largest potential for storing captured CO2 in the United Sates is in deep geologic saline formations. Currently, little is known about the effects of CO2 storage on biologically active microbial communities found in the deep earth biosphere. Therefore, to investigate how deep earth microbial communities will be affected by the storage of CO2 we have enriched for a microbial consortium from the saline formation waters of the Frio 2 project site (Texas Gulf Coast) that is capable of growth in nutrient media under a supercritical CO2 headspace (Hernandez, et al). The cultivation of actively growing cells in an environment containing scCO2 is unexpected based on previous experimental evidence of microbial sterilization attributed to the acidic, desiccating, and solvent-like properties of scCO2. We have isolated strain MIT0214 from this supercritical CO2 based enrichment and have sequenced its genome using the Illumina platform followed by de novo assembly of reads and targeted Sanger sequencing to reduce gaps in the draft assembly. The genome of strain MIT0214 is approximately 5,551,062 base pairs with 35% GC-content and is most similar to nonpathogenic Bacillus cereus strain ATCC 14597. Annotation of the draft assembly of the MIT0214 genome by the Rapid Annotation using Subsystem Technology (RAST) server revealed 5538 coding sequences where 4145 of the coding sequences were assigned putative functions. These functions were enriched in cell wall and capsule formation, phage/prophage and plasmids, gene regulation and signaling, and nitrogen and sulfur metabolism relative to the genome of the most closely-related surface-isolated B. cereus reference (ATCC 14597) and in total 773,416 bp of the MIT0214 genome content was distinct from the B. cereus reference. Notably, this set of distinct sequences were most similar to chromosomal and plasmid sequences from other closely-related Bacillus isolates, suggesting that strain MIT0214 has had access to the same flexible gene pool as other B. cereus isolates over its evolutionary history. Our findings suggest adaptation to a supercritical CO2 environment is not predicated on a high proportion of novel gene content and may simply reflect thermodynamic adaptations to growth under high pressure and differential regulation of genomic content widely distributed among Bacillus strains. Hernandez, H. H., Peet, K. C., Phelps, T. J., Pfiffner, S. M., Thompson, J. R. Microbial growth under supercritical CO2, submitted.