FIG. 2.

RpoS stability increases in response to carbon starvation independently of SprE phosphorylation. The half-life of RpoS was measured by Western blot analysis of samples taken before (time zero) and after the addition of chloramphenicol. Samples were taken from cells growing exponentially and from cells that had been immediately starved for carbon for 1 h. In both wild-type sprE (A) and sprED58A (B) backgrounds, RpoS is unstable during log phase and then its levels increase and it becomes stabilized upon glucose starvation. Likewise, RpoS-LacZ stability is regulated in a fashion similar to that of RpoS in the sprED58A strain (C). Above each lane, time (in minutes) after the addition of chloramphenicol is shown.