FIG. 8.

Changes in ATP, GTP, and (p)ppGpp by B. subtilis following entry into stationary phase in low or high PO₄ medium or amino acid limitation. Wild-type B. subtilis (BSA46) grown in synthetic medium with [³²P]H₃PO₄ (100 μCi/ml) for labeling nucleotides and either limiting (lanes 1 to 4) or nonlimiting PO₄ (lanes 5 to 11). At an optical density of 0.4, norvaline (1 mg/ml) and serine hydroxamate (1 mg/ml) were added to a portion of the culture with nonlimiting PO₄ (illustrated in lane 5) to mimic amino acid starvation. Samples were taken at 20-min intervals for both the untreated (lanes 6 to 8) and amino acid-limited (lanes 9 to 11) cultures. The low-PO₄ and high-PO₄ cultures ceased exponential growth at the times represented by lanes 3 and 7, respectively. Growth of the amino acid-limited cultures slowed by the first sample taken after the addition of the amino acid analogs (lane 9). Samples were analyzed by thin-layer chromatography as in Fig. 2.