Plate assay of phenol tolerance. Results of P. putida PaW85 (wt), colS-deficient (colS), colR-deficient (colR), ttgB-deficient (ttgB), ttgC-deficient (ttgC), colRttgB double mutant (colRttgB) and colRttgC double mutant (colRttgC) strains are presented. Approximately 1 × 105 cells were spotted onto solid medium and plates were incubated at 30°C for 48 hours. The minimal media contained either 10 mM glucose or 10 mM gluconate as the carbon source. Concentration of added phenol is indicated below the figures.