Our proposed research focuses on defining factors that limit antibiotic sensitivity of the chronic pathogen Heli- cobacter pylori. Evidence suggests that chronic H. pylori is difficult to cure with antibiotics because it is in a slow growth state controlled at least in part by stomach acid. H. pylori treatments rely on removing acid by in- cluding strong antacids called proton pump inhibitors (PPI). The PPI blocks acid production, raises the stom- ach pH, and promotes H. pylori growth. Bacterial growth allows standard antibiotics to work better. There is a gap in our understanding of the exact nature of the H. pylori chronic growth state, e.g. how active its metabo- lism is, whether acid is the only growth inhibitor, and what type of metabolism H. pylori deploys to grow after PPI treatment. This information is important because H. pylori infections are treated at the chronic state. Mil- lions of people worldwide and in the U.S. are infected by H. pylori and suffer from its associated diseases— ulcers and gastric cancer. Gastric cancer is the fourth leading cause of cancer deaths worldwide. H. pylori is an on-going problem, as the incidence has stabilized in the developed world. Furthermore, current therapies to cure H. pylori infection fail with unacceptable frequency: recent estimates in the United States have found that 20-25% of infected individuals are not cured by the current therapeutic regime. The overall objective of this ap- plication is to understand the H. pylori chronic growth state and use this information to design approaches that enhance growth and therefore antibiotic sensitivity. Our central hypothesis, based on published and preliminary data, is that the majority of chronic-state H. pylori are in an extreme slow growth mode, limited by a combination of acid, translational deficiency, and nutrient restriction. In Aim 1, we will use a combination of H. pylori mutants and mouse models to fill gaps in our understanding of the H. pylori chronic growth state and growth rate, how these parameters are affected by PPI, and whether post-PPI multiplication requires lactate utilization as early stage multiplication does. Additionally, we test whether increasing key carbon sources like lactate enhances H. pylori chronic state growth and antibiotic cure. In Aim 2, we build on preliminary data showing slow growth H. pylori display significant translational repression, including by increase in the riboso- mal silencing factor RsfS. We use molecular biology and biochemistry to fill gaps in our understanding of RsfS function in general, and to characterize how controlled RsfS expression, as well as other translational inhibi- tors, controls translation and affect chronic colonization. The proposed research is innovative in its hypothesis that H. pylori chronic slow growth is promoted by signals in addition to acid, and that knowing and targeting these will promote better cures. The proposed research is significant because it will provide new insi...