FIG 5.

The stringent response is required for survival in water and is affected by mutation of rpoS. (A) The stringent response mutant strain (relA spoT) and the wild-type strain (WT) were tested for survival in defined water (DFM) for 30 days at 25°C. CFU were counted every week on CYE plates. DL, detection limit of the CFU. (B) Cells retrieved from DFM were stained with 6 μM PI and 1 μM green fluorescing SYTO9 and then analyzed for cell viability with flow cytometry. We used an unpaired Student t test to assess statistical significance for each time point. **, P ≤ 0.005 (versus WT). (C) RT-qPCR was used to determine the level of expression of spoT and relA compared to the WT strain. The microarray data for the expression of spoT and relA (rpoS/WT) are indicated by black bars. The data are presented as the means of three biological replicates, and the error bars represent the standard deviations. Since the data represent a ratio against the WT strain, we used the nonparametric Mann-Whitney test to assess statistical significance. *, P ≤ 0.05 (versus WT).