Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
5 results
Search Results
Item Insights into the molecular mechanisms of sensing and responding to the host by Staphylococcus aureus(Montana State University - Bozeman, College of Agriculture, 2019) Meishery-Patel, Delisha; Chairperson, Graduate Committee: Jovanka Voyich-Kane; K. B. Pallister and Jovanka Voyich were co-authors of the article, 'Role of SaeR phosphorylation in regulation of Staphylococcus aureus virulence genes' which is contained within this thesis.; Dissertation contains an article of which Delisha Meishery-Patel is not the main author.Two-component systems (TCSs) are highly conserved across bacteria and are used to rapidly sense and respond to changing environmental conditions. The human pathogen Staphylococcus aureus uses the S. aureus exoprotein expression (sae) TCS to sense host signals and activate transcription of virulence factors essential to pathogenesis. Despite its importance, the mechanism by which the sensor kinase (SaeS) recognizes a stimulus and activates its cognate response regulator (SaeR) to regulate transcription of virulence genes is incompletely defined. However, findings from our lab suggest that SaeR/S mediated transcription is unique-to and dependent-on specific host stimuli. Studies outlined in this dissertation suggest that residues in the extracellular loop may be involved in refinement of the sae regulated targets at the single amino acid level. By generating single amino acid replacement mutants in the response regulator SaeR, we identified a key aspartate residue at position 46 (D46) on SaeR to be important in SaeR mediated signaling as mutation D46A prevented the recombinant protein from binding promoter recognition sequence and subsequently influenced virulence regulation. Current studies are aimed to define the phosphorylation patterns in SaeR using SDS-PAGE analysis and mass spectrometry. Overall, these structure-function studies provide insight into the Sae- signal transduction mechanism and raise some new questions regarding the role the Sae system in the larger regulatory network S. aureus uses to control expression of its secreted virulence factors.Item Diammonium phosphate as a source of nitrogen and phosphons for beef cattle(Montana State University - Bozeman, College of Agriculture, 1962) Cowman, Gary L.Item Structures of some phenyl phosphates(Montana State University - Bozeman, College of Letters & Science, 1964) Svetich, George WilliamItem Crystal and molecular structure of calcium 1-naphthyl phosphate trihydrate(Montana State University - Bozeman, College of Letters & Science, 1964) Li, JitangItem In situ microbial reduction of selenate in backfilled phosphate mine waste, s.e. Idaho(Montana State University - Bozeman, College of Agriculture, 2014) Kirk, Lisa Marie Bithell; Co-chairs, Graduate Committee: Tracy M. Sterling and Brent M. Peyton; Jared Bozeman and Susan E. Childers were co-authors of the article, 'Subsurface microbial selenium reduction by native consortia in phosphate mine waste, s.e. Idaho' submitted to the journal 'Applied and environmental microbiology' which is contained within this thesis.; Jared J. Bozeman, Brandy D. Stewart, Robin Gerlach and Brent M. Peyton were co-authors of the article, 'Kinetics of selenate reduction by native microbes in saturated phosphate mine waste' submitted to the journal 'Applied geochemistry' which is contained within this thesis.The reduction of selenium (Se) by microbes is controlled by oxygen (O 2)-availability within mixed deposits of shale, chert, and mudstone mined from the Phosphoria Formation in S.E. Idaho. Waste rock and groundwater from backfilled mine pits, which have been studied using geochemical, microbial cultivation, and molecular methods, host native populations of selenate-(SeO 4 2-) and selenite-(SeO 3 2-) reducing bacteria that are highly similar to the genera Dechloromonas, Stenotrophomonas, Anaeromyxobacter, and Ralstonia. These bacteria rapidly reduced more than 95% of soluble SeO 4 2- concentrations. Reduction occurred within a consortium of slow-growing, cold-tolerant, hydrocarbon-degrading, and nitrate-(NO 3-), iron-(Fe 3+), and manganese-(Mn 4+) reducing bacteria, including the genera Polaromonas and Rhodoferax, which appeared to use the naturally-occurring hydrocarbon present in the rock. Most-probable number estimates of SeO 4 2--reducers were highest in saturated sediments and in unsaturated shale, and were very low in unsaturated chert and mudstone. Selenium reduction was studied in microaerophilic, saturated native chert, shale, and mixed run-of-mine sediments inoculated with live groundwater cultures, with sampling and analysis of total Se, Fe, Mn; Se speciation; NO 3- and sulfate (SO 4 2-); dissolved organic carbon and total nitrogen(N); and mineralogy. Following an O 2- and N-dependent lag, SeO 4 2- was reduced within 100 hours under saturated, suboxic conditions at rates that varied depending on lithotype and temperature. The microbial community shifted during reduction as well, from phylotypes associated with the Fe-reducing Rhodoferax and HC-degrading Sphingomonas and SeO 4 2--reducing Dechloromonas genera to include members of the SeO 3 2-reducing genus Ralstonia. A unique biogeochemical Se reduction pathway was suggested in chert experiments, where Se reduction proceeded more rapidly and produced SeO 3 2- and elemental Se products, relative to the shale, wherein reduction was slower and produced more reduced selenide minerals. Results of these experiments offer insight into the results of in situ monitoring in backfill at multiple locations in S.E. Idaho, and potentially explain differences in Se solubility at these locations. Strategic management of rock and water in constructed mine wastefacilities to limit O 2 recharge can thus promote SeO 4 2- reduction by communities of indigenous organisms using available carbon and other electron donors. This offers a sustainable, design-based approach to natural attenuation of Se in mined rock.