Microbial Growth under Supercritical CO ₂

Abstract

Growth of microorganisms in environments containing CO 2 above its critical point is unexpected due to a combination of deleterious effects, including cytoplasmic acidification and membrane destabilization. Thus, supercritical CO 2 (scCO 2 ) is generally regarded as a sterilizing agent. We report isolation of bacteria from three sites targeted for geologic carbon dioxide sequestration (GCS) that are capable of growth in pressurized bioreactors containing scCO 2 . Analysis of 16S rRNA genes from scCO 2 enrichment cultures revealed microbial assemblages of varied complexity, including representatives of the genus Bacillus. Propagation of enrichment cultures under scCO 2 headspace led to isolation of six strains corresponding to Bacillus cereus, Bacillus subterraneus, Bacillus amyloliquefaciens, Bacillus safensis, and Bacillus megaterium. Isolates are spore-forming, facultative anaerobes and capable of germination and growth under an scCO 2 headspace. In addition to these isolates, several Bacillus type strains grew under scCO 2 , suggesting that this may be a shared feature of spore-forming Bacillus spp. Our results provide direct evidence of microbial activity at the interface between scCO 2 and an aqueous phase. Since microbial activity can influence the key mechanisms for permanent storage of sequestered CO 2 (i.e., structural, residual, solubility, and mineral trapping), our work suggests that during GCS microorganisms may grow and catalyze biological reactions that influence the fate and transport of CO 2 in the deep subsurface.

Thermodynamic and Kinetic Response of Microbial Reactions to High CO2

“…In addition, microbes survive better in aquifers capable of rapid pH buffering (Wu et al, 2010). Numerous studies have documented microbes in environments of elevated CO 2 , even microbial growth in the presence of supercritical CO 2 (Yakimov et al, 2002; Inagaki et al, 2006; Videmsek et al, 2009; Oppermann et al, 2010; Emerson et al, 2016; Peet et al, 2015). …”

Isolation and characterization of a CO2-tolerant Lactobacillus strain from Crystal Geyser, Utah, U.S.A.

“…This in turn, can complement existing genomic and metagenomic studies which can only confirm and infer the presence and activities of microbes based on sequence data. Previous culture-based approaches have also been performed utilizing samples from environmental sites (Mitchell et al, 2008;Kirk et al, 2013;Peet et al, 2015). Our approach was to work with a field site that had been under prolonged CO 2 perturbation (Burnside et al, 2013) to find out whether microbial communities under prolonged CO 2 exposure would still be viable.…”

Microbial potential for carbon and nutrient cycling in a geogenic supercritical carbon dioxide reservoir

“…At reservoir depths typically >1 km, CO 2 exists in the supercritical (sc) phase (31.18C, 72.9 atm). Although scCO 2 is regarded as a microbial sterilizing agent (White et al, 2006;Zhang et al, 2006;Mitchell et al, 2008;Ortuño et al, 2012), recent field and laboratory studies indicating resilience to stresses associated with supercritical (Mitchell et al, 2008;Mu et al, 2014;Peet et al, 2015) and near-critical CO 2 (de Beer et al, 2013;Emerson et al, 2015) suggest that scCO 2 -bearing reservoirs may support a stable microbial biosphere.…”