Fig. 4.

A putative divisor protein expressed from a constitutive promoter explains the shift data. (A) As model input, we used the measured instantaneous growth rates and volume-specific production rate $r$ (obtained from derivatives along lineages) from our promoters (in this case, the P5 constitutive promoter inserted close to the replication terminus). Note that this quantity has units ${\mathrm{m}\mathrm{i}\mathrm{n}}^{-1}$/$\mu {\mathrm{m}}^3$, minus a constant conversion factor from fluorescence to molecule number. The panel also shows the absolute fluorescence $F$ from the same promoter. A.u., arbitrary units. (B–D) The model predicts faithfully the size dynamics. (E) The model reproduces the observed robustness of near-adder size control. Other model variants using the production rates of different reporters fail to reproduce the observed size dynamics (SI Appendix, Figs. S6–S8). Data refer to average over biological replicates using the P5ter promoter strain (see Materials and Methods and SI Appendix, Figs. S6–S8 for the other strains).