FIGURE 1:

ppk1 is required for polyP granule production and survival in stationary phase. (A) Representative micrographs showing DAPI-stained log-phase WT C. crescentus and ∆ppk1 cells. Scale bars for this and subsequent micrographs, 1 μm. DAPI (polyP) images were taken with the same exposure and equally scaled for comparison. (B) Loss in viability of WT and ∆ppk1 complemented with xylose-inducible ppk1 (ppk1++) or an empty vector (EV) in M2X minimal medium after 24-h shaking in stationary phase. CFU/ml for three biological replicates of each strain plated upon entry to stationary phase and after 24-h culture in stationary phase; log change in CFU/ml from the initial plating to the 24-h plating is expressed on the y-axis. Dotted line, limit of detection (5 CFU/ml). Error bars, SE of the mean. *p < 0.001, Student's t test comparing the indicated strain with WT empty vector control (EV). Because zero CFU were isolated from ∆ppk1 EV cultures, error bars represent SE of the initial viability.