Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
2 results
Search Results
Item Rock powered life in the Samail ophiolite: an analog for early Earth(Montana State University - Bozeman, College of Agriculture, 2021) Fones, Elizabeth Marie; Chairperson, Graduate Committee: Eric Boyd; Daniel R. Colman, Emily A. Kraus, Daniel B. Nothaft, Saroj Poudel, Kaitlin R. Rempfert, John R. Spear, Alexis S. Templeton and Eric S. Boyd were co-authors of the article, 'Physiological adaptations to serpentinization in the Samail ophiolite, Oman' in the journal 'The International Society for Microbial Ecology journal' which is contained within this dissertation.; Daniel R. Colman, Emily A. Kraus, Ramunas Stepanauskas, Alexis S. Templeton, John R. Spear and Eric S. Boyd were co-authors of the article, 'Diversification of methanogens into hyperalkaline serpentinizing environments through adaptations to minimize oxidant limitation' in the journal 'The International Society for Microbial Ecology journal' which is contained within this dissertation.; David W. Mogk, Alexis S. Templeton and Eric S. Boyd were co-authors of the article, 'Endolithic microbial carbon cycling activities in subsurface mafic and ultramafic igneous rock' which is contained within this dissertation.Serpentinization is a geochemical process wherein the oxidation of Fe(II)-bearing minerals in ultramafic rock couples with the reduction of water to generate H 2, which in turn can reduce inorganic carbon to biologically useful substrates such as carbon monoxide and formate. Serpentinization has been proposed to fuel a subsurface biosphere and may have promoted life's emergence on early Earth. However, highly reacted waters exhibit high pH and low concentrations of potential electron acceptors for microbial metabolism, including CO 2. To characterize how serpentinization shapes the distribution and diversity of microbial life, direct cell counts, microcosm-based activity assays, and genomic inferences were performed on environmental rock and water samples from the Samail Ophiolite, Oman. Microbial communities were shaped by water type with cell densities and activities generally declining with increasing pH. However, cells inhabiting highly reacted waters exhibited adaptations enabling them to minimize stresses imposed by serpentinization, including preferentially assimilating carbon substrates for biomolecule synthesis rather than dissimilating them for energy generation, maintaining small genomes, and synthesizing proteins comprised of more reduced amino acids to minimize energetic costs and maximize protein stability in highly reducing waters. Two distinct lineages of a genus of methanogens, Methanobacterium, were recovered from subsurface waters. One lineage was most abundant in high pH waters exhibiting millimolar concentrations of H2, yet lacked two key oxidative [NiFe]-hydrogenases whose functions were presumably replaced by formate dehydrogenases that oxidize formate to yield reductant and CO 2. This allows cells to overcome CO 2/oxidant limitation in high pH waters via a pathway that is unique among characterized Methanobacteria. Finally, gabbro cores from the Stillwater Mine (Montana, U.S.A) were used to develop methods for detecting the activities of cells inhabiting mafic to ultramafic igneous rocks while controlling for potential contaminants. Optimized protocols were applied to rock cores from the Samail Ophiolite, where rates of biological formate and acetate metabolism were higher in rocks interfacing less reacted waters as compared with more extensively reacted waters, and in some cases may greatly exceed activities previously measured in fracture waters. This dissertation provides new insights into the distribution, activities, and adaptations exhibited by life in a modern serpentinizing environment.Item Structure and function of a prokaryotic argonaute from Pseudomonas aeruginosa(Montana State University - Bozeman, College of Agriculture, 2020) Erickson, Reece Sheridan; Chairperson, Graduate Committee: Blake WiedenheftArgonautes (Ago) are structurally and functionally diverse proteins present in all domains of life. A common feature of these ancient proteins is their ability to bind nucleic acid guides that target the protein to complementary sequences. Although eukaryotic argonautes (eAgo) have been well-studied, we still know very little about the function of prokaryotic argonautes (pAgo) in bacterial and archaeal species. To address this gap in our knowledge, my thesis focused on determining the biochemical properties as well as the cellular functions of a pAgo from the organism Pseudomonas aeruginosa PACS2 (PaAgo). Here, we show that PaAgo plays a role in regulating the expression of transposons within PACS2. I also present results indicating that deletion of the PaAgo gene and its neighboring genes causes toxicity to P. aeruginosa. Finally, I provide evidence that PaAgo and a neighboring protein are binding partners and form a multi-protein complex. Future work will focus on copurifying and sequencing PaAgo nucleic acid guides as well as clarifying the mechanisms guide acquisition and biological function.