The specific objective of my research program is to develop a better understanding of the pathogenesis, ecology, evolution, and transmission of bacterial foodborne and zoonotic diseases. The pathogenesis of foodborne and zoonotic diseases can involve complex interactions between a bacterial pathogen, a variety of environments and one or multiple host species. The ability of bacterial cells to survive and compete in a variety of environments plays a key role in the pathogenesis and transmission of many foodborne diseases. In addition, selective pressures not associated with mammalian hosts may contribute significantly to the emergence and evolution of virulence characteristics related to the ability of bacteria to effectively infect mammalian hosts. Foodborne zoonotic pathogens provide ideal model systems for studying the ecology of infectious diseases, including adaptation of clonal groups to specific hosts and non-host environments as well as virulence gene expression and maintenance of virulence characteristics under widely varying conditions, including those not directly associated with a host.