In addition to its role as a nutrient, the essential iron acts as a regulatory signal to control synthesis of iron acquisition systems, certain toxins, and a variety of other bacterial proteins. Thus iron is one of a number of environmental stimuli to which cells respond. The long range goals of this project are to characterize the genetics and regulation of iron acquisition and other systems associated with in vivo survival of Shigella, an enteric bacterium which multiplies both extracellularly and intracellularly within host intestinal epithelial cells. These studies will include (1) characterizing genes and gene products which are differentially expressed in vivo and the associated regulatory signals, (2) measuring the expression of iron-regulated genes in an in vivo system, and (3) characterizing the genetics and regulation of Congo red/heme binding (crb). Experimental approaches will utilize genetic and biochemical techniques. In vivo expression of the genes will be investigated using fusions to reporter genes whose expression can be readily monitored , and an in vivo labeling system has been developed to compare proteins synthesized by bacteria inside host cells to those observed in vitro. Mutants with altered gene regulation will also be characterized. These studies will help define mechanisms of regulation both in vivo and in vitro.
