We grew Pseudomonas aeruginosa biofilms on CFBE41o- human airway cells in culture, and we treated these biofilms with tobramycin. Microarray analysis was performed to gain an understanding of the global transcriptional changes that occur during antibiotic treatment. Experiment Overall Design: We compared three untreated control samples with three tobramycin-treated samples. Biofilms were grown on CFBE41o- cells in culture for 9 hours in MEM/0.4% arginine. Replicate samples were then incubated in the presence or absence of 500 μg/mL tobramycin for 30 minutes.