FIG. 4.

RpoS is partially stabilized during phosphate deprivation in both the sprE⁺ and sprED58A backgrounds. The half-life of RpoS was measured by Western blot analysis of samples taken before and after addition of chloramphenicol. Samples were taken from cultures that had been immediately starved for 1 h for carbon or phosphate. RpoS behaved similarly in both the sprE⁺ (A and closed symbols in panel C) and the sprED58A (B and open symbols in panel C) strain backgrounds but was not completely stabilized after phosphate deprivation, as it was after carbon starvation. Above each lane, time (in minutes) after the addition of chloramphenicol is shown. Quantification of the RpoS levels is shown in panel C, with circles representing carbon starvation and squares representing phosphate starvation.