The ability of heme proteins to reversibly bind diatomic ligands allows organisms to sense changes in their environment. Recently, changes in gaseous ligand concentrations have been proposed to be involved in the pathogenesis of a variety of bacteria. Our work focuses on understanding how the globin coupled sensor protein family senses oxygen and transmits the binding signal into downstream events. Understanding how these diatomic signals are transduced will elucidate the role of heme sensors in bacterial signaling pathways and pathogenesis, as well as potentially yield starting points for the development of novel antibacterial agents.