Every motile cell and organism is able to monitor and track its chemical environment, a behavior known as chemotaxis. The chemotaxis machinery of bacterial cells like Escherichia coli enables them to move toward beneficial chemicals (attractants) and away from harmful ones (repellents). The "central processing unit" of the E. coli chemotaxis machinery is the CheA signaling protein. In my project, I created mutant CheA proteins in a 6-residue domain linker that is important for CheA signaling activity. I assessed the CheA mutant chemotaxis phenotypes on soft agar plates. Some residues supported chemotaxis; others did not. I plan to evaluate the cellular amounts and stability of CheA protein in each mutant. Stable CheA proteins were tested for their ability to regulate intracellular signaling activity in response to chemical stimuli. Further characterization of the functional defects of the mutated CheA domain will enable me to test a working model of CheA signaling.