Expression profiling of Pseudomonas aeruginosa in chronic wound exudate media

Transcriptomic, metabolomic, physiological, and computational modeling approaches were integrated to gain insight into the mechanisms of antibiotic tolerance in an in vitro biofilm system. Pseudomonas aeruginosa biofilms were grown in drip-flow reactors on a medium composed to mimic the exudate from a chronic wound (CWE). After 72 hours, the biofilms were treated with CWE (control biofilms) or CWE containing ciprofloxacin (treated biofilms) for an additional 24 hours. Planktonic samples were cultivated to early logarithmic phase in CWE. The biofilm specific growth rate was estimated via elemental balances to be approximately 0.37 h-1, or one-third of the planktonic maximum specific growth rate. Global analysis of gene expression indicated decreased anabolic activity in biofilms compared to planktonic cells. A focused transcriptomic analysis revealed the induction of multiple stress responses in biofilm cells, including those associated with growth arrest, zinc limitation, hypoxia, and acyl-homoserine lactone quorum sensing. Three biological replicates were prepared and analyzed for the following three growth conditions: (1)Pseudomonas aeruginosa was grown planktonically to early log phase. (2) Pseudomonas aeruginosa was grown in drip flow biofilm reactors on hydroxyapetite-coated glass slides for four days. (3) Pseudomonas aeruginosa was grown in drip flow biofilm reactors on hydroxyapetite-coated glass slides for three days and then treated with 1 mg/ml ciprofloxacin for an additional day.