Model parameters

This protocol is extracted from research article:

Concurrent processes set E. coli cell division

**
Sci Adv**,
Nov 7, 2018;
DOI:
10.1126/sciadv.aau3324

Concurrent processes set E. coli cell division

Procedure

We discuss here the values of the model parameters used in the plots and how they were fixed. The cyan lines in Fig. 2C represent theoretical predictions and have a negative slope corresponding to Eq. 8 with *p*_{H} = 0.48, 0.3, and 0.75 for an adder between initiations (see below), respectively, for the Wallden *et al*. slow growth, Adiciptaningrum *et al*., and Wallden *et al*. intermediate growth datasets (*6*, *12*). These values were fixed from Fig. 2A and Eq. 8. The same values of *p*_{H} are used in all other plots. In Fig. 2D, the orange lines are the best fit for the case where replication is limiting [corresponding to the model of (*7*)]. The average duration of the C + D period is set from the empirical averages to 160, 102, and 75 min for the Wallden *et al*. slow growth, Adiciptaningrum *et al*., and Wallden *et al*. intermediate growth datasets, respectively. Cyan curves follow Eq. 9 with *p*_{H} fixed as above, and *et al*. slow growth), 52 min (Adiciptaningrum *et al*.), and 41 min (Wallden *et al*. intermediate growth).

Figure 3 (B and D) shows the result of numerical simulations, where the parameters were constrained from the data. The plots in Fig. 2 fix the values of *p*_{H} and ^{−1} to match the experimental values. The variance of the growth rate was chosen by keeping a constant coefficient of variation (CV) of 0.15. The growth rate was a normal or log-normal random variable (the two choices do not affect the results, see below), extracted independently for every cell cycle. (iii and iv) The average added volume per origin between consecutive initiations 〈*ν*_{I}〉 and its variance ^{3} as measured in (*6*), and the variance was fixed to a constant CV of 0.15. The added volume between consecutive initiations was assumed to be log-normally distributed (and extracted independently for every cell cycle). (v and vi) The average time needed for replication and segregation (the C + D′ period) _{H}〉 and its variance _{H}〉 sets the characteristic size of the interdivision process _{H}〉 was fixed to achieve the same values of *p*_{H} as in Fig. 2 (B and D). In Fig. 3D, the interdivision added volume was fixed so that for the case of concurrent cycles, the replication-related process and the interdivision process would compete to set division in the same way across all conditions. Specifically, we chose 〈Δ_{H}〉 = 〈*ν*_{I}〉 exp(45 min ⋅ 〈α〉) for the case of concurrent processes (Fig. 3D, cyan line). The case where replication is never limiting (purple line) was simulated by assuming the same 〈Δ_{H}〉 but setting _{H}〉 = 0 to simulate the case of replication always limiting (orange line). With these choices, *p*_{H} ≈ 0 for the replication always limiting case (Fig. 3D, orange line), *p*_{H} ≈ 0.6 for concurrent cycles (cyan line), and *p*_{H} ≈ 1 for the replication never limiting models (purple line). The variance

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