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. Author manuscript; available in PMC: 2020 Jun 3.
Published in final edited form as: Curr Biol. 2019 May 16;29(11):1760–1770.e7. doi: 10.1016/j.cub.2019.04.062

Figure 5: The mechanistic origin of the adder and validation.

Figure 5:

(A) The adder phenotype requires accumulation of division proteins to a fixed amount 2N* to trigger division, and their balanced biosynthesis during growth. Under these conditions, newborn cells are born either larger or smaller than the population average, but they on average contain N* division proteins. The two adder requirements ensure that both small-born and large-born cells add a constant size (namely, N* division proteins) in each generation.

(B) A typical timelapse sequence with FtsZ-mVenus. The total intensity was obtained by integrating the FtsZ-mVenus fluorescence intensity over the entire cell, which increases steadily from birth to division, tracking elongation of the cell. As a result, the FtsZ-mVenus concentration stays nearly constant within fluctuations.

(C) The synthesis and accumulation of FtsZ in E. coli cells fulfills both requirements for adder. The total added FtsZ number ΔN (estimated by the added fluorescence ΔI) and the synthesis per unit volume dN/dS were constant and independent of cell size at birth.

See also Figure S5 and Methods S1.