The interaction between amoebae and bacteria is one of oldest predator-prey relationships in nature and a major driving force for bacterial diversity, persistence, and pathogenesis. The amoebae ingest the bacteria and enclose them in a compartment for degradation. The bacterium Legionella pneumophila resists degradation by changing the membrane-bound compartment so that it can proliferate. This intracellular survival strategy is common to many bacteria, however, the mechanisms that underlie this strategy are not well understood. The research supported by this award will define the molecular mechanisms through which Legionella controls and manipulates the eukaryotic cell and resists degradation. This information will lead to novel insights into how bacteria are able to survive within eukaryotic cells, including immune cells such as macrophages. As such, this research has the potential to provide a better understanding of bacterial pathogenesis. The educational goal of this project is to stimulate interest in science at multiple educational levels with a focus on retention of students from underrepresented minority groups. This goal will be accomplished by partnering with the Upward Bound Math/Science program at the University of Delaware to stimulate enthusiasm for scientific research by providing high school students with authentic research experiences, developing a research-based module to enhance the current undergraduate microbiology curriculum at the University of Delaware, and developing and implementing interactive materials and hands on activities for families attending the Delaware Children's Museum. Since diverse undergraduate and graduate students will participate in these community outreach activities, children will observe that people of various ages and ethnicities can be scientists. This project is co-funded by the Symbiosis, Defense, Self-recognition Program in the Division of Integrative Organismal Systems and by the Established Program to Stimulate Competitive Research.
In nature, amoebae ingest bacteria by phagocytosis, and once internalized, bacteria remain enclosed in a plasma membrane-derived compartment that is destined for degradation by fusion with lysosomes. However, L. pneumophila remodels the cytosolic surface of the vacuolar membrane to avoid degradation. The integrity and remodeling of the vacuole is critical for survival of L. pneumophila and its establishment requires the activity of bacterial proteins delivered into the host cell via a specialized secretion system. The overarching hypothesis of this project is that remodeling of the replication-permissive vacuole depends on the bacterium's ability to target and regulate host membrane trafficking. The principal investigator will apply microbiological, biochemical, and cell biological approaches to determine the molecular mechanisms that bacterial proteins use to selectively target host vesicles in order to promote bacterial survival. The focus is on refining our understanding of how bacterial proteins manipulate the activity of two key components that regulate host vesicular traffic: Rab GTPase proteins and phosphoinositide lipids. Results obtained here will advance the field of host-microbe interactions by further defining how free-living bacteria can acquire the capacity to grow within eukaryotic cells. The project will provide educational opportunities for URM high-school and undergraduate students and will facilitate interactions between students and the local community through outreach activities.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
