Carbon Sources

AB medium (3 g/L K₂HPO₄, 0.3 g/L MgSO₄⋅7H₂O, 1 g/L NH₄Cl, 0.15 g/L KCl, 1 g/L NaH₂PO₄, 0.01 g/L CaCl₂, 0.0025 g/L FeSO₄⋅7H₂O, 5 g/L casein hydrolyzed amino acids) was prepared as previously described (Zimmer et al., 2014). The overnight culture of P. fluorescens PF08 (OD₅₉₅ = 1) was diluted 1:100 in prepared AB culture medium, followed by the addition of 5 g/L of different carbon sources (glucose, xylose, sucrose, fructose, lactose, or maltose). All samples were incubated at 28°C until an OD₅₉₅ of 1 was reached. After centrifugation at 8000 × g for 10 min, the cells were collected for the analysis of rhlI/R transcription level using qPCR. Samples incubated in LB broth at 28°C were the control.