title: CO2 exposure at pressure impacts metabolism and stress responses in the model sulfate-reducing bacterium Desulfovibrio vulgaris strain Hildenborough.
abstract: Geologic carbon dioxide (CO2) sequestration drives physical and geochemical changes in deep subsurface environments that impact indigenous microbial activities. The combined effects of pressurized CO2 on a model sulfate-reducing microorganism, Desulfovibrio vulgaris, have been assessed using a suite of genomic and kinetic measurements. Novel high-pressure NMR time-series measurements using (13)C-lactate were used to track D. vulgaris metabolism. We identified cessation of respiration at CO2 pressures of 10 bar, 25 bar, 50 bar, and 80 bar. Concurrent experiments using N2 as the pressurizing phase had no negative effect on microbial respiration, as inferred from reduction of sulfate to sulfide. Complementary pressurized batch incubations and fluorescence microscopy measurements supported NMR observations, and indicated that non-respiring cells were mostly viable at 50 bar CO2 for at least 4 h, and at 80 bar CO2 for 2 h. The fraction of dead cells increased rapidly after 4 h at 80 bar CO2. Transcriptomic (RNA-Seq) measurements on mRNA transcripts from CO2-incubated biomass indicated that cells up-regulated the production of certain amino acids (leucine, isoleucine) following CO2 exposure at elevated pressures, likely as part of a general stress response. Evidence for other poorly understood stress responses were also identified within RNA-Seq data, suggesting that while pressurized CO2 severely limits the growth and respiration of D. vulgaris cells, biomass retains intact cell membranes at pressures up to 80 bar CO2. Together, these data show that geologic sequestration of CO2 may have significant impacts on rates of sulfate reduction in many deep subsurface environments where this metabolism is a key respiratory process.
authors.affiliation: Pacific Northwest National Laboratory, Biological Sciences Division Richland, WA, USA ; Department of Microbiology, School of Earth Sciences, The Ohio State University Columbus, OH, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wilkins
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Hoyt
authors.affiliation: Pacific Northwest National Laboratory, Biological Sciences Division Richland, WA, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Marshall
authors.affiliation: Pacific Northwest National Laboratory, Biological Sciences Division Richland, WA, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Alderson
authors.affiliation: Pacific Northwest National Laboratory, Biological Sciences Division Richland, WA, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Plymale
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: L Meng
authors.initials: LM
authors.lastname: Markillie
authors.affiliation: Pacific Northwest National Laboratory, Biological Sciences Division Richland, WA, USA.
authors.forename: Abby E
authors.initials: AE
authors.lastname: Tucker
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Walter
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Linggi
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: Alice C
authors.initials: AC
authors.lastname: Dohnalkova
authors.affiliation: Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory Richland, WA, USA.
authors.forename: Ron C
authors.initials: RC
authors.lastname: Taylor
keywords: Desulfovibrio vulgaris; NMR spectroscopy; RNA-Seq; geologic CO2 sequestration; microbial stress