Demonstrating biocompatibility with supercritical CO₂ : biphasic cultivation of Bacillus spp. and probing acclimation mechanisms through proteome and lipid analysis
Author(s)
Peet, Kyle Creighton![Thumbnail](/bitstream/handle/1721.1/97795/911926690-MIT.pdf.jpg?sequence=3&isAllowed=y)
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Massachusetts Institute of Technology. Department of Civil and Environmental Engineering.
Advisor
Janelle R. Thompson.
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Supercritical (sc) CO₂ usage is increasing globally with applications as a sterilizing agent, as a non-toxic solvent, and as the form of the greenhouse gas CO₂ injected underground for geologic carbon sequestration (GCS). In this thesis I have described the isolation of microorganisms from three different carbon sequestration pilot sites through a novel method of successive scCO₂ enrichments. I show that microorganisms of the genus Bacillus, including GCS site isolates, are resistant to the bactericidal properties of scCO₂ , and can germinate and grow in an aqueous phase incubated under scCO₂ (Chapter 2). Bacterial resistance to scCO₂ challenges the efficacy of scCO₂ based sterilization and indicates that microbial activity may be harnessed in engineered environments containing scCO₂ (e.g. biochemical catalysis involving scCO₂ as a solvent or biofilm/biomineralized barriers to scCO₂ leakage from GCS sites). In an effort to understand the physiology of acclimation to scCO₂, I have sequenced and analyzed the genomes of two GCS-site isolates, B. cereus MIT0214 and B. subterraneus MITOTI (Chapter 3). I have used genome-enabled analysis of the proteome combined with analysis of membrane lipids to ask whether cellular macromolecules are differentially represented in cells grown under different headspace and pressure conditions including CO₂ and scCO₂ (Chapters 4). In this chapter I have examined the following three hypotheses regarding the mechanisms employed by Bacilli to resist scCO₂ : (1): Resistance to CO₂ stress is governed by a similar response as acclimation to low pH stress. (2): Cell wall and membrane alterations promote bacterial growth under scCO₂ by modulating the cell's microenvironment. (3): Global expression of proteins mediating cellular homeostasis in viable but non-growing (stationary-phase) populations acclimated to scCO₂ resembles a generalized profile of anaerobic growth, with notable exceptions of individual protein(s) that mediate acclimation. The results from this thesis enhance understanding of bacterial resistance to scCO₂, enabling improved strategies for scCO₂-based sterilization and accelerating biotechnological applications of scCO₂-biocompatible organisms.
Description
Thesis: Ph. D. in Environmental Biology, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015. Cataloged from PDF version of thesis. Includes bibliographical references (pages 136-152).
Date issued
2015Department
Massachusetts Institute of Technology. Department of Civil and Environmental EngineeringPublisher
Massachusetts Institute of Technology
Keywords
Civil and Environmental Engineering.