FIG. 6.

The sprED58A mutation is additive with Δ(ackA-pta). Western blot samples were taken from exponentially growing cells in LB and M63 minimal glucose media. The single mutant sprED58A and the double mutant sprED58A Δ(ackA-pta) had higher RpoS levels than the Δ(ackA-pta) single mutant in minimal medium, indicating that acetyl phosphate is not the sole phosphodonor for SprE. In LB medium, the additivity seen in the double mutant compared to the single mutants suggests that the lack of acetyl phosphate affects another mechanism of RpoS regulation, most likely synthesis.