Theses and Dissertations at Montana State University (MSU)
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Item Investigating arsenic-microbiome interactions in the gut using murine models(Montana State University - Bozeman, College of Letters & Science, 2019) Coryell, Michael Philip; Chairperson, Graduate Committee: Seth Walk; B. A. Roggenbeck and Seth T. Walk were co-authors of the article, 'The human gut microbiome's influence on arsenic toxicity' submitted to the journal 'Current pharmacology reports' which is contained within this thesis.; M. McAlpine, N.V. Pinkham, T.R. McDermott and Seth T. Walk were co-authors of the article, 'The gut microbiome is required for full protection against acute arsenic toxicity in mouse models' in the journal 'Nature communications' which is contained within this thesis.; M. Yoshinaga, T.R. McDermott and Seth T. Walk were co-authors of the article, 'Speciation of excreted arsenicals from germ free and conventional AS3MT knockout mice exposed to inorganic arsenate' which is contained within this thesis.Drinking water contamination with arsenic is a wide-spread public health concern, potentially affecting over 140 million people across at least 40 different countries. Current understanding of biological and behavioral factors influencing clinical outcomes is insufficient to explain the variation observed in arsenic-related disease prevalence and severity. The intestinal microbiome in humans is a dynamic and active ecosystem with demonstrated potential to mediate arsenic metabolism in vitro and distinct variability between individuals. This dissertation investigates arsenic-microbiome interactions, with a focus on determining how microbiome activity influences host-response and toxicity from arsenic exposures. Chapter 2 overviews common exposure routes, important metabolic pathways, and current evidence of arsenic-microbiome interactions in humans or experimental animal models. Chapter 3, the initial approach was to experimentally perturb the microbiome of common laboratory mice during arsenic exposure, measuring arsenic excretion in the stool and accumulation in host tissues. Arsenic sensitive gene-knockout mice were used to determine the microbiome's influence on subacute arsenic-induced mortality. Disrupting microbiome function--first by antibiotic treatment, then by deriving mice germ free--dramatically reduced survival times during severe arsenic exposures. Transplantation of human fecal communities into germ free mice effectively complemented the loss of function from microbiome disruption in these mice. Chapter 4 examines microbiome's impact on arsenic metabolism in germ free and conventional mice from this same arsenic-sensitive genetic background. These mice are deficient for the primary metabolic pathway involved in arsenic detoxification in both humans and mice, facilitating a more complete experimental isolation of microbiome and host metabolisms. This study provides evidence of microbiome-dependent changes in the elimination routes and metabolic transformation of ingested arsenic and provides a new experimental model for studying arsenic metabolism in the gut.Item Kinetics of biofilm growth and substrate uptake in model drinking water systems(Montana State University - Bozeman, College of Engineering, 1998) Butterfield, Phillip WesleyItem Pathogens in model distribution system biofilms(Montana State University - Bozeman, College of Agriculture, 1996) Warnecke, Malcolm RobertItem Factors influencing biofilm growth in drinking water distribution systems(Montana State University - Bozeman, College of Engineering, 1995) Camper, Anne KosteczkoItem Application of the biofilm coupon as a direct measure of the in situ growth potential of water(Montana State University - Bozeman, College of Agriculture, 1995) Bakich, Shannon GaylordItem Comparison of models for bacterial regrowth in water distribution systems(Montana State University - Bozeman, College of Engineering, 1995) Nichols, Naomi Ruth WrightItem Application of the biofilm coupon to bacterial regrowth potential(Montana State University - Bozeman, College of Engineering, 1993) Xu, XiaomingItem Changes in the virulence of chlorine-injured Yersinia enterocolitica(Montana State University - Bozeman, College of Agriculture, 1985) LeChevallier, Mark WilliamItem Growth of mycobacterium avium in dual species biofilms with Pseudomonas aeruginosa(Montana State University - Bozeman, College of Letters & Science, 2007) Karmacharya, Amresh Prasad; Chairperson, Graduate Committee: Tim E. FordInterest in the growth of M. avium in biofilms has increased in the last few years. Research has shown that M. avium cells in biofilms are more resistant to disinfectants than their planktonic counterparts. Although M. avium has been detected in biofilms in in situ and laboratory models, information available on M. avium is limited compared to biofilm model species such as Pseudomonas aeruginosa, Escherichia coli, Staphylococcus and Streptococcus. The main objective of the present research was to study the growth of M. avium in biofilms in the presence of P. aeruginosa. Biofilms were grown in sterile tap water on stainless steel coupons in batch mode. Two kinds of reactors were used; mason jars and a recirculation system. Each experiment lasted from 27 to 35 days depending upon the nature of the experiment. The two strains were inoculated in isolation (monospecies) and also in combination (dual species).