FIG. 3.
Life span of P-starved cells depends upon the limiting concentration of Pi in the medium. Strain ENZ535 (wt) grown overnight in complete MOPS medium containing 5 mM K2HPO4 was inoculated 1:500 (time zero) into MOPS media containing 40 mM glucose and various limiting concentrations of K2HPO4, including 25 μM (□), 40 μM (▵), 70 μM (○), and 100 μM (⋄), plus KCl to maintain the K+ concentration at 10 mM. The cultures were incubated with aeration for 17 days. Parentheses indicate that no CFU were detected when 20-μl portions of the cultures were directly plated. The values are the means ± standard deviations for two independent cultures. On day 17 of incubation, the OD600 (pHs) of the cultures were 0.32 (pH 4.97), 0.43 (pH 4.83), 0.63 (pH 4.74), and 0.84 (pH 4.70) with 25, 40, 70, and 100 μM Pi, respectively.