M9 sythetic medium: 48 mM Na2HPO4, 22 mM KH2PO4, 10 mM NaCl, 40 mM (NH4)zSO4 and 4 g/l of glucose. Components filter-sterilized separatory and then added (per liter of final volume): 1 ml 1 M MgSO4, 1 ml vitamin B1 (1 mgl stock), 1 ml 0.1 mM CaCl2, and 10 ml trace element solution containing (per liter): 0.55g CaCl2 1g FeCl3, 0.1 mg/l MnCl2.4H2O, 0.17 g ZnCl2, 0.043 g CuCl2.2H2O, 0.06 g CoCl2.2H2O, and 0.06 g Na2MoO4.2H2O).

Cells were separated from the culture by centrifugation at 10,000 ×g for 15 min at 0°C. To extract intracellular metabolites from the cell pellet, 500 ml of 50% methanol was added, and the cells were re-suspended by vortexing the mixture. Then 2 ml of 35% of perchloric acid ... was added, which was pre-cooled on ice, and vortexed again for 10 s. After one freeze-thaw cycle, proteins and cell fragments were removed by centrifugation at 12,000 ×g for 30 min at 0°C. Clear suparnatant was neutralized by adding collected supernatant, and then 895 μm of 5 M K2KO3 was added. Precipitated perchlorates were removed by another centrifugation step (12,000 ×g at 0°C for 10 min), the clear supernatant was collected, and they were stored as 200 μm aliquots at -20°C for analysis.