| Helicobacter pylori is a Gram-negative, spiral-shaped, microaerophilic bacterium that establishes life-long infections of the gastric mucosa causing gastritis, peptic ulcers, MALT lymphomas and increases the risk of gastric cancer. The remarkable ability of H. pylori to survive the acidic environment of the stomach and chronic inflammation is bestowed by a strong urease and a diverse antioxidant defense system. Unfortunately, the genetics of Helicobacter are not easily manipulated, therefore, advancements in its biology has been hindered by the lack of genetic tools. The aim of this study was to evaluate fundamental mechanisms involved in the colonization of H. pylori in the gastric mucosa. This theme was divided into two areas where we: (i) demonstrated that H. pylori senses pH, possibly through the methyl-accepting chemoreceptor protein TlpB, and responds using tactic behavior which is essential for mouse colonization and; (ii) delineated the role of the antioxidant AhpC during colonization. In the latter, we developed a novel antisense RNA interference strategy to target and knockdown AhpC protein levels between 30 and 74%. These knockdowns correlated with increased sensitivity to oxidative stress, however, did not alter the efficiency to colonize the mouse stomach. To further the application of antisense RNA, antisense constructs were also constructed to target two essential two-component regulators, HP0166 (ArsR) and HP1043 which are thought to be involved in acid resistance and the regulation of tlpB, respectively. Knockdowns were achieved with the former while several attempts to knockdown HP1043 were unsuccessful. This work demonstrates a fundamental process (pH taxis) probably involved during initial colonization of H. pylori to a new host and that the host oxidative defense system may not be a barrier for initial colonization. Additionally, the application of antisense RNA technology is a useful tool for the evaluation of gene function in H. pylori and may provide a way forward for the study and characterizing factors involved in colonization and pathogenesis. |
