FIG. 5.

In logarithmic phase, phosphorylation of SprE contributes to its basal activity. (A) Western blot of samples taken during logarithmic-phase growth in minimal glucose medium. RpoS levels with SprED58A are at an intermediate level between the wild type and the sprE null strain. (B) Western blot of half-life samples taken during log-phase growth in M63 minimal glucose medium. Above each lane, time (in minutes) after the addition of chloramphenicol is shown. (C) Quantification of the RpoS levels shown in panel B, with the wild-type strain represented by closed squares, the sprED58A strain represented by open diamonds, and the sprE null strain represented by closed triangles. The RpoS half-life was calculated to be 4.7-fold longer with SprED58A than with the wild type, yet there is substantial SprE activity remaining compared to that in the sprE null strain.