Stenotrophomonas maltophilia is an emerging, multidrug-resistant Gram-negative bacterium that infects the lungs of cystic fibrosis (CF) patients. Infected patients have an increased risk of death and are more likely to require antibiotics and lung transplants. S. maltophilia is often isolated from patients that also harbor pathogens like Pseudomonas aeruginosa and Staphylococcus aureus. We are interested to understand how CF S. maltophilia isolates compete against other bacterial pathogens and we are studying the molecular mechanisms used by S. maltophilia to engage in antagonistic behaviors.