Mammalian innate immune cells take up and kill invading bacteria via phagocytosis; however, pathogenic bacterial strains have evolved means to evade killing upon phagocytic uptake to escape innate immune defense. The soil amoeba Dictyostelium discoideum also uses phagocytosis to take up bacteria for nutritive purposes. Bacteria in the soil that have evolved mechanisms to evade D. discoideum predation enjoy a selective advantage, and many of these resistance mechanisms are similar to those used by bacteria to evade mammalian innate immune defense. This project tests the hypothesis that the selective advantage gained against D. discoideum predation upon development of these resistance mechanisms may have contributed to coincidental evolution of bacterial virulence factors against mammalian hosts. Therefore, investigation of bacterial mechanisms used to evade D. discoideum predation could lead to identification of novel bacterial virulence factors and host factors required for bacterial killing, which once identified can be used as targets for development of anti-bacterial therapies. The use of next generation sequencing technology provides a powerful tool for genomic and transcriptomic analyses of the interactions between D. discoideum and its bacterial prey. This fellowship application seeks to support a sabbatical for Dr. Snyder in the laboratory of Dr. Rasko at the University of Maryland Institute for Genome Sciences in order to incorporate into Dr. Snyder's studies of D. discoideum/bacterial interactions genomic and transcriptomic approaches, for which Dr. Rasko has extensive expertise.
The specific aims of the project are to 1) analyze the genomes of bacterial strains that have evolved resistance to D. discoideum predation and 2) compare the transcriptomic responses of D. discoideum cells and bacterial prey both in cases in which the bacteria have and have not evolved resistance to killing upon D. discoideum phagocytosis. These studies will inform the investigators on the molecular mechanisms underlying host-pathogen interactions and should lead to insight on the evolution and maintenance of bacterial virulence factors and mechanisms to evade the phagocytic process. Completion of this project will also establish collaborations between the laboratories of Dr. Snyder and Dr. Rasko and will provide Dr. Snyder training so that she can develop projects that will expose undergraduate and masters-level graduate students to genomics research both in her research laboratory and in authentic research-based laboratory courses at Towson University.
This study makes use of next generation sequencing technologies to characterize the molecular mechanisms underlying host responses associated with efficient clearance of bacteria as well as the strategies used by bacteria to block host defense responses. Given the deficiencies in small animal models for the majority of the human enteric pathogens, the development of the Dictyostelium discoideum model system offers a significant advantage for studies of host-enteric interactions. The proposed research will provide vital mechanistic insight that is difficult or impossible to obtain any other way and that will infrm studies that will lead to the development of therapies that block bacterial virulence mechanisms or alter host responses to elicit those most effective for clearing bacterial infections.