FIG 4.

Cellular spermidine levels in Pseudomonas aeruginosa PAO1 and its derivatives. The intracellular spermidine molecules were benzoyled and examined by liquid chromatography coupled with mass spectrometry (LC-MS). The P. aeruginosa PAO1 and derivatives were cultured in LB (A and D), LBN (B and E), and MMN (C and F) as indicated. Bacterial cells were harvested for assay of spermidine levels when bacterial cell density reached OD₆₀₀ of 0.5, 1.0, 1.5, and 2.0, respectively. The experiment was repeated at least triplicates in each assay and error bars indicate standard deviations.