Nucleic acid modifications in bacterial pathogens - impact on pathogenesis, diagnosis, and therapy

Abstract

Nucleic acids are subject to extensive chemical modification by all organisms. These modifications display incredible structural diversity, and some are essential for survival. Intriguingly, several of these modifications are unique to bacteria, including many human pathogens. Given the enormous global disease burden due to bacterial infections, and the rapidly increasing rates of antibiotic resistance reported across the world, the need for research to address mechanisms of bacterial survival is more pressing than ever. The goal of this thesis was to determine the function of nucleic acid modifications in pathogenic bacteria, and to evaluate their impact on the three major stages of the infectious disease process: pathogenesis, diagnosis, and therapy. We first used quantitative profiling of tRNA modifications to identify novel stress responses that help mediate host invasion in the world's most common pathogen, Helicobacter pylori. This work uncovered potentially novel targets for the development of new compounds that inhibit pathogenesis. We then developed a new animal model of mycobacterial lung infection that enables drug development and biomarker screening studies in standard laboratories without high-containment facilities. We showed that infection with Mycobacterium bovis bacille Calmette-Guérin produces a granulomatous lung disease in rats that recapitulates many of the important pathological features of human tuberculosis. This model also allowed us to test the utility of nucleic acid modifications as diagnostic biomarkers. Finally, we investigated the effect of the common, transferable bacterial DNA modification phosphorothioation on oxidative and antibiotic stress responses in several pathogens. We showed that phosphorothioation can reduce the effectiveness of antibiotic therapy, which may make it an environmental source of acquired antibiotic resistance. These studies show that nucleic acid modifications play diverse roles in pathogenic bacteria, and that their modulation may be a promising target for developing new tools that can disrupt pathogenesis, improve diagnosis, and strengthen therapy.