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

Abstract

SummaryMicroorganisms catalyze carbon cycling and biogeochemical reactions in the deep subsurface and thus may be expected to influence the fate of injected supercritical (sc) CO2 following geological carbon sequestration (GCS). We hypothesized that natural subsurface scCO2 reservoirs, which serve as analogs for the long‐term fate of sequestered scCO2, harbor a ‘deep carbonated biosphere’ with carbon cycling potential. We sampled subsurface fluids from scCO2‐water separators at a natural scCO2 reservoir at McElmo Dome, Colorado for analysis of 16S rRNA gene diversity and metagenome content. Sequence annotations indicated dominance of Sulfurospirillum, Rhizobium, Desulfovibrio and four members of the Clostridiales family. Genomes extracted from metagenomes using homology and compositional approaches revealed diverse mechanisms for growth and nutrient cycling, including pathways for CO2 and N2 fixation, anaerobic respiration, sulfur oxidation, fermentation and potential for metabolic syntrophy. Differences in biogeochemical potential between two production well communities were consistent with differences in fluid chemical profiles, suggesting a potential link between microbial activity and geochemistry. The existence of a microbial ecosystem associated with the McElmo Dome scCO2 reservoir indicates that potential impacts of the deep biosphere on CO2 fate and transport should be taken into consideration as a component of GCS planning and modelling.

Insights into microbial community structure and function from a shallow, simulated CO2‐leakage aquifer demonstrate microbial selection and adaptation

“…A limited number of studies have shed light on the functional potential of microorganisms in naturally occurring subsurface CO 2 sites. Freedman and colleagues () performed metagenomic analysis on separator fluids from wells at depths of 1800–2600 m in the CO 2 exposed McElmo Dome, Colorado, and identified microbial pathways that could change ecosystem function such as carbon fixation via the Wood Ljungdahl pathway and Calvin Benson cycle, nitrogen and sulfur oxidation and fermentation (Freedman et al ., ). Probst and colleagues () assessed the fluids from the Crystal Geyser in Utah and also demonstrated carbon fixation potential via the Wood Ljungdahl pathway and Calvin Benson cycle, sulfur oxidation and partial nitrogen reduction.…”

Isolation, Development, and Genomic Analysis ofBacillus megateriumSR7 for Growth and Metabolite Production Under Supercritical Carbon Dioxide

“…Fluids from three CO 2 production wells at McElmo Dome, previously shown by microscopy 335 to contain biomass (Freedman et al, 2017), were used as inocula for enrichment culture under scCO 2 . 336…”

“…To be considered feasible for industrial 82 bioprocess development, it is required for strains to remain biocompatible with scCO 2 in a batch or 83 continuous flow bioreactor over a time period of days to weeks. In light of this requirement, recent 84 attention has focused on several research efforts that have identified microbial populations resilient 85 over extended periods of exposure to scCO 2 in natural (Mu et al, 2014;Freedman et al, 2017) and 86 laboratory (Mitchell et al, 2008) systems, including in aqueous media under scCO 2 headspace (Peet 87 et al, 2015). 88…”

“…McElmo Dome CO 2 Field in Cortez, Colorado, where scCO 2 has accumulated over 40-72 million 98 years (Cappa and Rice, 1995;Gilfillan et al, 2008). Since previous work has revealed evidence of an 99 anaerobic microbial ecosystem (Freedman et al, 2017) we hypothesized that organisms isolated from 100 this site may demonstrate enhanced scCO 2 -resistance and growth potential. 101…”

The defining genomic and predicted metabolic features of the Acetobacterium genus

“…Sulfate reducing bacteria (SRB) are often found in these environments as well, with several studies suggesting a syntrophic partnership between SRB and acetogens [15,16]. In particular, a combination of Desulfovibrio, Sulfurospirillum, and Acetobacterium were proposed to cooperatively participate in microbial induced corrosion (MIC) of steel [16], have been found in production waters from a biodegraded oil reservoir [17], and can be detected in natural subsurface CO 2 reservoirs [18]. Moreover, these three microorganisms were the most abundant members of the biocathode community responsible for electrode-driven production of acetate and hydrogen from CO 2 [19][20][21].…”