Figure 5. Ribosomes are stabilized in non-growing non-protein synthesizing cells.

(A). Ribosomes containing the destabilizing 23S rRNA A1919G mutation are stable in the stationary growth phase. A1919G mutants were grown in inducing conditions (arabinose) to early stationary phase, labeled with [H³] uridine for 45 minutes, and switched to exhausted medium with repressor (glucose). Exhausted medium was collected from a culture grown for 24 h before removing the cells by centrifugation. First time point was collected 1 hour after the medium switch. This correspond to 25 hours, or 1500 min as shown on the figure (n = 2). (B). Inhibition of protein synthesis stabilizes the ribosomes. Cell culture expressing the pHyb1919G mutant was grown under inducing conditions until OD₆₀₀ = 0.2, labeled for 30 minutes with [H³]-uridine, after which the growth medium was exchanged for glucose-containing LB (repressing medium). 30 minutes after medium switch chloramphenicol (100 µg/ml) was added (n = 4). The first time point was taken 30 minutes after chloramphenicol addition (labeled in the figure as 60 min from medium switch).