Bacterial protein sample preparation, 2-D gel and MS analyses were performed as follows. P. putida UW4 was cultivated aerobically to late-log phase in Tryptic Soy broth (Fisher Scientific Co., Ottawa, ON) at 30˚C. First, bacterial cells were harvested by centrifugation at 8,000 g at 4°C for 10 minutes. The pellets were washed twice with cold water and weighed. The cell pellet was resuspended in ice-cold lysis buffer (2 M thiourea, 7 M urea, 4% w/v CHAPS, 30 mM Tris pH 8.5; 5 mL/g wet cells). The cells were then stirred at 4°C for 30 minutes. The lysate was centrifuged at 10,000 g at 4°C for 10 minutes. The final supernatant was saved as the whole cell extract and stored at –70°C until it was used.