Fig. (3) Natural abundance ¹³C-nuclear magnetic resonance spectra of ethanolic extracts from P. aeruginosa PAO1 cells grown (A) in NaCl-free PPGAS medium, (B) in PPGAS containing 0.5 M NaCl, (C) in PPGAS/NaCl with 1 mM glycine betaine (GB) until exponential phase, or (D) in PPGAS/NaCl/GB until stationary phase. In (A) and (B) conditions, identical spectra were obtained from cells in exponential and stationary phase. Resonances due to glutamate (G), N-acetylglutaminylglutamine amide (D), trehalose (T), and GB are indicated. Unidentified peaks corresponding to none of the possible osmoprotectants are labelled “?”.