Using Dictyostelium discoideum as a model for phagocytosis resistance in Escherichia coli

Abstract Escherichia coli related illnesses continue to be a problem around the world, especially in developing countries that lack clean water and proper sanitation. Dictyostelium discoideum is a soil dwelling amoeba that phagocytizes bacteria for nutrients. D. discoideum is a great model to study host pathogen interactions, and it has been used to identify virulence factors in bacteria. Our objective is to use Dictyostelium discoideum as a model to identify bacterial genes involved in resistance to phagocytosis. We hypothesize that D. discoideum can be used as a model organism to identify virulence genes associated with E. coli. The aims of this study are to identify E. coli genes predicted to grant resistance to D. discoideum grazing and phagocytosis and further characterize genes identified as potential virulence factors and observe the genes’ effects on D. discoideum grazing and phagocytic killing. Intestinal pathogenic, extraintestinal pathogenic, and laboratory E. coli strains were classified according to grazing phenotype. Previous comparative genomic analysis by large-scale BLAST score ratio (LS-BSR) identified genes prevalent amongst strains resistant to D. discoideum grazing. The gene gipA (growth in Peyer’s patches) was one gene found in various E. coli strains resistant to D. discoideum grazing. We are currently working to characterize the role of E. coli genes associated with resistance to D. discoideum grazing by manipulating E. coli strains for expression of these genes. We will observe the interactions between these strains and D. discoideum grazing and phagocytosis. This experiment will give insight into bacterial genes and virulence factors responsible for evading phagocytosis and the immune system. This project was funded in part by federal funds from the National Institute of Allergy and Infectious Diseases, National Institute of Health, and Department of Health and Human Services under grant number U19 AI110820. Dr. M. Snyder was funded by an NIH NIGMS grant F33 GM116618, a Franklin Research Grant from the American Philosophical Society and a grant from the TU FDRC committee. This research was also supported by an NIH NIGMS R25 GM19970.