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Identification and Characterization of Histoplasma capsulatum extracellular proteins and their roles in virulenceHolbrook, Eric 18 December 2012 (has links)
No description available.
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The Oxidative Stress Defenses of Campylobacter jejuniFlint, Annika January 2015 (has links)
Campylobacter jejuni infection is one of the leading causes of gastroenteritis in humans worldwide. During colonization of the gastrointestinal tract, C. jejuni will be unavoidably exposed to reactive oxygen species (ROS) produced by the host immune system and other intestinal microbiota. Identification of defenses against ROS is therefore important for understanding how Campylobacter survives this environmental stress during infection. Construction of isogenic deletion mutants into genes encoding potential oxidative stress defense systems followed by phenotypic screening revealed genes important for oxidant defense within C. jejuni. Surprisingly, genes involved in motility were found to play an indirect role in resistance to oxidative stress. Deletion of the flagellar motor apparatus genes, motAB, resulted in increased sensitivity towards superoxide which could be restored by fumarate supplementation or tandem deletion of motAB with ccoQ (cytochrome c oxidase). This finding suggested that disruption of the proton gradient across the inner membrane resulted in increased superoxide production in non-motile flagellar mutants. Phenotypic screening of the mutant library also identified a novel gene (cj1386) specifically involved in hydrogen peroxide defense within the cell. Hydrogen peroxide detoxification within living organisms is predominantly carried out by catalase enzymes. Interestingly, cj1386 is located directly downstream from katA (catalase) in the C. jejuni genome and it was found that a ∆cj1386 mutant had reduced catalase activity relative to wild-type C. jejuni. Immunoprecipitation of KatA from ∆cj1386 revealed a significant reduction in hemin content associated with KatA suggesting a role for cj1386 in hemin trafficking to KatA. Hemin binding experiments with purified Cj1386 demonstrated the ability of Cj1386 to bind hemin with a 1:1 hemin-to-protein binding ratio. Furthermore, co-immunoprecipitation experiments revealed an interaction between KatA and Cj1386. Mutagenesis of conserved amino acids in Cj1386 demonstrated that tyrosine 57 plays an important role in hemin affinity and is required for proper hemin content of KatA within the cell. Overall, this work provides a global characterization of key oxidant defenses within C. jejuni and provides one of the first studies investigating hemin trafficking to KatA.
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Dietary Restriction-Induced Longevity in Caenorhabditis elegans: Mediated by Stress Defense, NAD\(^+\)-Dependent Mechanisms and a Respiratory ShiftKaragodsky, Natalie January 2014 (has links)
Dietary restriction (DR), or the reduction of food consumption without malnutrition, is the most conserved method of preventing or reversing age associated diseases. It is also the most conserved method of increasing lifespan, across model organisms. We developed a robust liquid DR method for C. elegans, to investigate requirements for stress defense and NAD\(^+\)-associated mechanisms in mediating DR induced longevity. We found that DR lifespan extension depended upon stress defense regulators that act downstream of TORC1 and growth pathways, as well as SIR-2.1/SIRT1 and the NAD\(^+\) salvage pathway enzyme PNC-1. Surprisingly, PNC-1 was not required for improvement in two measures of healthspan, or the period of life spent free from disease. This suggests that the genetic regulation of DR effects can be uncoupled from one another, and that increased healthspan does not always indicate increased lifespan.
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