Motile bacteria have evolved sophisticated information processing capabilities that when coupled to the power of the bacterial flagellar motor, allow cells to move toward or away from a chemical stimulus in a process known as chemotaxis.  The ability to engineer bacteria to move toward new ligands will provide new opportunities in nanotechnology by enabling bacteria to carry loads toward a chemical stimulus; in medicine by enabling bacteria to localize to a disease site; and in environmental remediation by enabling bacteria to swim toward and degrade pollutants.  Molecular recognition of chemical stimuli in E. coli is performed by a series of five chemoreceptors on the surface of the cell.  While using protein engineering to change the ligand specificity of these receptors is possible, structural constraints enforced by the protein scaffolds, and the potential for crosstalk between receptors with overlapping ligand specificities makes this a very challenging protein engineering problem.  We will show that using RNA, rather than proteins, to recognize new small molecule ligands allows us to bypass these challenges.  Using a ligand-dependent synthetic riboswitch to activate the translation of a single gene, we have engineered E. coli to follow a desired chemical stimulus.  These engineered cells recapitulate many of the chemotactic behaviors of natural E. coli, including the ability to sense and respond to chemical gradients.  In addition, these cells are able to localize to the desired chemical stimulus, which allows the spatial targeting of cells.  We anticipate that bacteria engineered to follow new chemicals will facilitate new developments in synthetic biology.