Fig 5. Maintenance ribosomes are responsible for the increase in active ribosomes in the presence of degradation.

(a) Theoretical curves (in the combined model) of the maintenance ribosome fraction as a function of the degradation rate η for different fixed growth rates λ. Crosses and circles are obtained from experimental data in E. coli and S. cerevisiae respectively. Since f_bm is a function of the ratio η/λ only, the inset shows that such curves collapse if plotted as a function of the degradation-to-growth rate ratio. (b) Maintenance ribosome fraction as a function of growth rate estimated from data, for S. cerevisiae and E. coli. The fraction of maintenance ribosomes is mathematically identical to the relative difference in total active ribosome fraction between the degradation-only model and the standard framework without degradation. Equivalently, the fraction of active ribosome increases in the presence of degradation due to maintenance ribosomes. Degradation data were derived from [38] (E. coli) and [42] (S. cerevisiae). Total ribosome fraction data used in Eq (19) to estimate f_bm come from [5] (E. coli) and [4] (S. cerevisiae).