Many bacteria are exposed to a variety of environments during their lifecycles. These environments may be both inside and outside the host, and particular signals in these environments may activate expression of genes that result in changes that allow the bacterium to cope more effectively with the specific environment. One of the current aims of research in the R-J lab is to understand how symbiotic bacteria survive in many distinct environments, including those encountered during the course of interaction with the host, by identifying and characterizing genes that are expressed in each environment. Additionally, the R-J lab has become increasing interested in focusing on a very specialized niche for bacterial life, that of the intracellular environment of a eukaryotic cell. Thus, our primary research aim is to determine the physiological requirements for bacteria to live within the eukaryotic host (especially in the intracellular environment) and the bacterial gene regulation in the host environment.
From 2002-2013, the model system that the R-J lab initially used use to address these problems was the facultative intracellular bacterium Shigella flexneri, which encounters many different environments during its journey through the external environment and human host. More information can be found here about this work.
Beginning in 2006, The R-J lab began working with a second intracellular bacterium that lives inside eukaryotic cells. This bacterium, Sodalis glossinidius, is a facultative intracellular bacterium that is a secondary symbiont of the tsetse fly. The Sodalis genome has recently been sequenced, and the bacterium is phylogenetically related to E. coli. We plan to use this bacterium as a model organism to address the question “What are the physiological requirement for intracellular life, regardless of type of endosymbiosis?”. Our current work focuses on the role and regulation of iron acquisition and heme-iron tolerance mechanisms of Sodalis.
Work in the R-J lab currently has been supported by the National Institutes of Health, the Thomas F. Jeffress and Kate Miller Jeffress Memorial Trust, and the University of Richmond School of Arts and Science.