Comparative Ribosome Analysis of Pseudomonas aeruginosa Planktonic and Biofilm Cells

Pseudomonas aeruginosa is an opportunistic pathogen commonly found in the lungs of cystic fibrosis patients. P. aeruginosa is notable for its ability to form biofilms within the lungs. Biofilms exhibit incredible antibiotic tolerance. Tolerance differs from resistance: while resistant cells may actively grow in the presence of antibiotics, tolerant cells slow their metabolic rates, preventing most antibiotics from taking effect. The tolerance of P. aeruginosa biofilms is the cause of recalcitrant infections in cystic fibrosis infections. In this project, we sought to characterize the ribosomes of P. aeruginosa planktonic and biofilm cells in samples which either have or have not been exposed to tobramycin. Tobramycin is an aminoglycoside commonly used in P. aeruginosa infections. Recent studies have shown environmental stressors including antibiotic exposure cause ribosome degradation, remodeling, and dimerization in E. coli, leading to translational inhibition and in turn, antibiotic tolerance. We hypothesized similar events occur in tolerant cells of P. aeruginosa. We isolated ribosomes of planktonic and biofilm cells through sucrose gradient centrifugation. Following this, we qualified the relative distributions of ribosome fractions and analyzed the protein makeup of these ribosomes by mass spectrophotometry. We expect to observe a difference between the protein makeup of ribosomes from biofilm cells and those from planktonic cells. We expect similar results between samples treated with/without tobramycin. The results of this project may mediate future research on how to target cells exhibiting antibiotic tolerance.