FIG. 2.

Induction of (p)ppGpp synthesis by amino acid limitation. Congenic B. subtilis strains BSA46 (RelA⁺) [lanes 1 to 3] and BSZ7 (relA3-542) [lanes 4 to 6] and BSJ18 (RelA⁺) [lanes 7 to 9] and BSJ19 (relA240GE) [lanes 10-12] were grown to optical density 0.3 in synthetic medium with Casamino Acids and ³²[P]H₃PO₄ (100 μCi/ml), pelleted and resuspended in the same medium without Casamino Acid but with norvaline (1 mg/ml). Samples were taken at 20 min (lanes 1, 4, 7, and 10), 40 min (lanes 2, 5, 8, and 11), and 60 min (lanes 3, 6, 9, and 12) after resuspension and analyzed by thin-layer chromatography as described in Materials and Methods. The positions of ATP and GTP were determined with nucleotide markers. The (p)ppGpp positions were inferred from their mobilities relative to GTP (13).