The ability of an organism to perceive its environment and to respond accordingly is a key survival factor for any species. An important example of environmental sensing is the evolution of antibiotic resistance among bacteria, which is a significant challenge for fighting and containing infections in hospital and community settings. These adaptations by disease-causing bacteria allow them to sense the presence of drugs and respond by producing agents to resist the antibiotic. Multidrug resistant bacterial strains have emerged and are increasing in frequency, making treatment more costly and such infections more lethal. Dr. Gerd Prehna is studying the structures and pathways within bacteria that enable this to happen. He is studying in salmonella a novel antivirulence pathway that regulates bacterial populations within the host. Disruption of this process would lead to an unorganized effort by a bacterial infection to maintain itself within a host, reducing its ability to cause illness. He is also studying methicillin resistant staphylococcus aureus, or MRSA, which has evolved a complex sensor molecule that binds to antibiotics and then relays a signal for the bacteria to express resistance factors. By solving the complete three-dimensional structure of this antibiotic sensor, he hopes to determine the mechanism by which this signal is relayed. By learning more about how disease-causing bacteria detect antibiotics, communicate with each other, and collectively mount a defense against these drugs, Prehna hopes this knowledge might be exploited to block sensory and communication pathways, making the bacteria once more susceptible to antibiotics.