Despite of a boost of recent progress in dynamic single-cell measurements and analyses in E. coli, we still lack a mechanistic understanding of the determinants of the decision to divide. Specifically, the debate is open regarding the hierarchy of processes linking growth and chromosome replication to division, and on the molecular origin of the observed "adder correlations", whereby cells divide adding roughly a constant volume independent of their initial volume. In order to gain insight into these questions, we interrogate dynamic size-growth behavior of single cells across nutrient upshifts with a high-precision microfluidic device. We find that the division rate changes quickly after nutrients change, much before growth rate goes to a steady state, and in a way that adder correlations are robustly conserved. Comparison of these data to simple mathematical models falsifies proposed mechanisms where replication-segregation or septum completion are the limiting step for cell division. Instead, we show that the accumulation of a putative constitutively expressed "P-sector divisor" protein explains the behavior during the shift.

中文翻译：

---

组成型蛋白质的阈值积累解释了在营养上调中大肠杆菌细胞分裂行为。

尽管在大肠杆菌中动态单细胞测量和分析的最新进展有所提高，但我们仍然对决定分裂的决定因素缺乏机械理解。具体而言，关于将生长和染色体复制与分裂联系起来的过程的层次以及关于观察到的“加法相关性”的分子起源的争论是公开的，由此细胞分裂增加了一个恒定的体积，而与它们的初始体积无关。为了深入了解这些问题，我们使用高精度的微流控装置询问营养物上移过程中单个细胞的动态大小增长行为。我们发现，在营养变化后，生长速度远未达到稳定状态之前，分度率变化很快，并且以可靠地保持加法器相关性的方式。将这些数据与简单的数学模型进行比较会伪造所提出的机制，其中复制-分离或隔垫完成是细胞分裂的限制步骤。取而代之的是，我们证明了一个假定的组成性表达的“ P扇形除数”蛋白的积累解释了这一转变过程中的行为。