RNase II regulates RNase PH and is essential for cell survival during starvation and stationary phase

Survival of wild-type and mutant cells during starvation. WT, RNase II⁻, RNase PH⁻, and RNase II⁻ RNase PH⁻ strains were first grown in M9/glucose media at 31°C to an A₆₀₀ of ∼0.2, and then subjected to starvation in M9 salts at either 31°C or 42°C as described in Materials and Methods. At regular time intervals, appropriate sequential dilutions of cells in duplicate were spread on LB plates and viable cells (CFU) were determined after overnight incubation at 37°C. Data are presented as a percentage in which the zero time of starvation was set at 100%. A representative experiment from those repeated two or three times is shown.