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1. Grégoire, Daniel. Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction .

Degree: 2019, University of Ottawa

Mercury (Hg) is a global pollutant and potent neurotoxin that bioaccumulates in aquatic and terrestrial food webs as monomethylmercury (MeHg). Anaerobic microbes are largely responsible for MeHg production, which depends on the bioavailability of inorganic Hg substrates to methylators. Hg redox cycling pathways such as Hg reduction play a key role in determining Hg’s availability in the environment. Although abiotic photochemical Hg reduction typically dominates in oxic surface environments, Hg reduction pathways mediated by photosynthetic and anaerobic microbes are thought to play an important role in anoxic habitats where light is limited and MeHg production occurs. Currently, the physiological mechanisms driving phototrophic and anaerobic Hg reduction remain poorly understood. The main objective of my thesis is to provide mechanistic details on novel anaerobic and phototrophic Hg reduction pathways. I used a combination of physiological, biochemical and trace Hg analytical techniques to study Hg reduction pathways in a variety of anaerobic and photosynthetic bacteria. I demonstrated that Hg redox cycling was directly coupled to anoxygenic photosynthesis in aquatic purple non-sulphur bacteria that reduced HgII when cells incurred a redox imbalance. I discovered that terrestrial fermentative bacteria reduced Hg through pathways that relied on the generation of reduced redox cofactors. I also showed that sulphur assimilation controlled Hg reduction in an anoxygenic phototroph isolated from a rice paddy. In addition, I developed methods to explore cryptic anaerobic Hg redox cycling pathways using Hg stable isotope fractionation. At its core, my thesis underscores the intimate relationship between cell redox state and microbial Hg reduction and suggests a wide diversity of microbes can participate in anaerobic Hg redox cycling.

Subjects/Keywords: Mercury; Redox cycling; Anaerobic bacteria; Photosynthetic bacteria; Heliobacteria; Purple non-sulphur bacteria; Stable isotope fractionation; Sulphur assimilation; Redox homeostasis; Anoxygenic photosynthesis; Bioremediation; Climate change; Fermentation

…140 Chapter 5: Heliobacteria reveal fermentation as a key pathway for mercury reduction in… …Heliobacterium modesticaldum Ice1, a thermophilic representative from the family Heliobacteria… …Heliobacteria are a metabolically versatile family of terrestrial spore-forming obligate anaerobes… …decision to work with Heliobacteria was motivated by the fact that many Heliobacteria isolates… …Heliobacteria strain with a sequenced genome 73. The objective in Chapter 6 was to build on the… 

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APA (6th Edition):

Grégoire, D. (2019). Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction . (Thesis). University of Ottawa. Retrieved from http://hdl.handle.net/10393/38722

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Grégoire, Daniel. “Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction .” 2019. Thesis, University of Ottawa. Accessed August 11, 2020. http://hdl.handle.net/10393/38722.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Grégoire, Daniel. “Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction .” 2019. Web. 11 Aug 2020.

Vancouver:

Grégoire D. Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction . [Internet] [Thesis]. University of Ottawa; 2019. [cited 2020 Aug 11]. Available from: http://hdl.handle.net/10393/38722.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Grégoire D. Photosynthetic and Fermentative Bacteria Reveal New Pathways for Biological Mercury Reduction . [Thesis]. University of Ottawa; 2019. Available from: http://hdl.handle.net/10393/38722

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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