References and Notes

in a cell cycle–dependent manner. Only four of these (DivJ, CckA, PleC, and CheA) have been characterized, and three of the four (boxed in Fig. 4) are known to be dynami-cally localized to the cell poles at different times in the cell cycle (21, 22). The spatial distribution of CtrA also varies during the cell cycle (Fig. 1A) (20); together, these ob-servations add another regulatory dimension. The operation of Caulobacter’s genetic cir-cuitry controlling cell cycle progression and asymmetric cell division must ultimately be analyzed and modeled as an integrated, three-dimensional system of coupled chemical re-actions incorporating genome-scale informa-tion on mRNA and protein levels, posttrans-lation modifications, and spatial distributions