Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
5 results
Search Results
Item Omics approaches identify molecular mechanisms of arsenic-microbial interactions(Montana State University - Bozeman, College of Letters & Science, 2019) Rawle, Rachel Anna; Chairperson, Graduate Committee: Timothy R. McDermott and Brian Bothner (co-chair); Yoon-Suk Kang, Brian Bothner, Gejiao Wang and Timothy R. McDermott were co-authors of the article, 'Transcriptomics analysis defines global cellular response of Agrobacterium tumefaciens 5A to arsenite exposure regulated through the histidine kinases phor and aios' in the journal 'Environmental microbiology' which is contained within this dissertation.; Monika Tokmina-Lukaszewska, Zunji Shi, Brian Tripet, Fang Dang, Timothy R. McDermott, Valerie Copie, Gejiao Wang and Brian Bothner were co-authors of the article, 'Metabolic responses to arsenite exposure regulated through histidine kinases phor and aios in Agrobacterium tumefaciens 5A' submitted to the journal 'Environmental microbiology' which is contained within this dissertation.Arsenic is a class I carcinogen and causes various cancers and diseases. Its toxicity, prevalence, and potential for human exposure has classified arsenic as the number one environmental toxin according to the Environmental Protection Agency. Contamination of groundwater and soil leads to over 200 million human exposures above the health limit. In every environment where arsenic and microbes coexist, microbes are the principal drivers of arsenic speciation, which is directly related to bioavailability, toxicity, and bioaccumulation. These speciation events drive arsenic behavior in the soil, water, and as recent data suggests, human-associated microbiomes. This dissertation details arsenic-microbial interactions through an omics platform, utilizing transcriptomics, metabolomics, and proteomics profiling as a way to globally assess the impacts of arsenic exposure. This work followed two main aims: (1) characterize cell metabolism during arsenic exposure in soil bacterium Agrobacterium tumefaciens 5A, a model organism for arsenite oxidation, and (2) assess the impacts of specific arsenic-processing bacteria within the gut microbiome of mammals. The results of this work provide a foundational understanding for how arsenic speciation events are regulated and how they affect nutrient cycling in environmental systems, which is necessary for bioremediation and health initiatives.Item Chromatographic, spectroscopic and microscopic analyses reveal the impact of iron oxides and electron shuttles on the degradation pathway of 2,4,6- trinitrotoluene (TNT) by a fermenting bacterium(Montana State University - Bozeman, College of Agriculture, 2003) Borch, Thomas; Chairperson, Graduate Committee: William P. Inskeep and Robin Gerlach (co-chair)Contamination of surface and subsurface environments with explosives such as 2,4,6-trinitrotoluene (TNT) is a worldwide problem. The fate and analysis of TNT were investigated in numerous artificially contaminated model systems. We developed a unique high performance liquid chromatography gradient elution method for the analysis of commonly observed TNT metabolites and EPA explosives. Column temperature was identified as the key parameter for optimal separation. Iron (hydr)oxides play an important role in the reduction, sorption and fate of TNT in soil and sediment. Consequently, characterization of the nature and properties of natural and synthetic Fe (hydr)oxides is important for determining reaction mechanisms and surface-associated chemical processes. This work thus summarizes the potential applicability of imaging and spectroscopic techniques for eliciting chemical and physical properties of iron (hydr)oxides. TNT is persistent in soils due to its low redox potential and sorption. Batch and column studies revealed some of the first results on TNT desorption behavior in two well-defined model soil systems. Biosurfactants were found to be the most promising technique for enhanced TNT desorption. Batch studies with a Cellulomonas sp. in the presence of ferrihydrite and the electron shuttle anthraquinone-2,6-disulfonate (AQDS) were conducted to reveal biotic and abiotic mechanisms contributing to the degradation of TNT. Strain ES6 was found to reduce TNT and ferrihydrite with enhanced reduction in the presence of AQDS. Ferrihydrite stimulated the formation of more reduced TNT metabolites such as 2,4-diamino-6-nitrotoluene. Interestingly, a completely different degradation pathway was observed in AQDS-amended iron-free cell suspensions, showing a rapid transformation of TNT to 2,4-dihydroxylamino-6-nitrotoluene, which transformed into unidentified polar products. The influence of iron phases (i.e. hematite, magnetite, and ferrihydrite) and secondary Fe mineral formation on the degradation of TNT was also evaluated. The initial reduction of TNT was fastest in the presence of hematite; however, the further reduction of hydroxylamino-dinitrotoluenes was fastest, in the presence of magnetite and ferrihydrite (no AQDS). The impact of AQDS was predominant in the presence of hematite resulting in the formation of 2,4,6-triaminotoluene. Ferrihydrite underwent reductive dissolution with the formation of secondary hematite. The enhanced TNT reduction in ferfihydrite-amended systems was therefore most likely due to redox-active Fe(II) rather than secondary Fe phases.Item Using the root zone water quality model (RZWQM) to predict water movement through a hydrocarbon contaminated soil(Montana State University - Bozeman, College of Engineering, 2003) Anderson, Scott Michael; Chairperson, Graduate Committee: Otto R. SteinItem Alkaline industrial by-product effects on plant growth in acidic-contaminated soil systems(Montana State University - Bozeman, College of Agriculture, 2002) Mehlenbacher, Joel ThomasItem Impact of a model soil on the biotransformation of 2,4,6-trinitrotoluene and its amine metabolites(Montana State University - Bozeman, College of Engineering, 2004) Walker, Diane Kathryn; Chairperson, Graduate Committee: Alfred B. CunninghamThe end of the Cold War resulted in the closure of many sites where explosives were manufactured, processed, and stored, and packaging practices left behind highly contaminated surface waters, groundwater and soils. Chief among the explosives contaminating these sites is the xenobiotic, 2,4,6- trinitrotoluene (TNT) whose electron-withdrawing nitro-groups make this aromatic compound highly resistant to biodegradation. An alternative option to mineralization as a bioremediation strategy, however, is immobilization. TNT can be biotransformed under reducing conditions to 2,4,6-triaminotoluene (TAT), a compound that researchers are currently investigating due to its potential to become irreversibly bound to soil components. The objectives of this research were to conduct TNT biotransformation studies under planktonic conditions and compare the results to those under slurry conditions. These objectives would also contribute to the overall goals of a DEPSCoR-sponsored project entitled "Biofilm-Induced Changes in Soil Organic Matter Structure and the Resulting Impact on the Bioavailability of Sorbed 2,4,6-Trinitrotoluene and its Amine Metabolites". Three experiments were performed for this research. The first was to create a model soil that was both well-characterized yet chemically representative of real soil constituents. The second was to add TNT to actively growing Desulfovibrio sp. strain SHV and monitor TAT formation. The third was a combination of the first two experiments, adding strain SHV to the model soil to both observe TAT formation and its disappearance from solution over time. The results of the TNT biotransformation studies indicated that TNT was transformed to TAT, which became the dominant metabolite in four weeks under planktonic conditions. Under slurry conditions, TAT became the dominant metabolite in two days and disappeared from solution by day three.