P. aeruginosa has been studied extensively for over 100 years due to its role in chronic infections of the urinary tract, pneumonia in cystic fibrosis patients, its ability to delay wound healing, and in foreign-body infections (biomaterial implants and devices such as catheters and prosthetics).2,4,14-17 Biofilm-based chronic infections caused by P. aeruginosa affect millions of people and are the leading cause of morbidity and mortality in patients suffering from cystic fibrosis.18,19 Growth in biofilms is associated with an increased mutation rate, known as the mutator phenotype, which is thought to contribute to antibiotic resistance.6,7,9 This mutator phenotype is characterized by a few to one thousand-fold the mutation frequency of the common laboratory strain (PAO1).9,20-22 However, it is not currently known what controls P. aeruginosa biofilm growth or how biofilm growth activates the mutator phenotype.6,7,9,23-25 Although it has been suggested that genes that…