Lampo Thomas J, Kuwada Nathan J, Wiggins Paul A, Spakowitz Andrew J
Department of Chemical Engineering, Stanford University, Stanford, California.
Departments of Physics and Bioengineering, University of Washington, Seattle, Washington.
Biophys J. 2015 Jan 6;108(1):146-53. doi: 10.1016/j.bpj.2014.10.074.
The physical mechanism by which Escherichia coli segregates copies of its chromosome for partitioning into daughter cells is unknown, partly due to the difficulty in interpreting the complex dynamic behavior during segregation. Analysis of previous chromosome segregation measurements in E. coli demonstrates that the origin of replication exhibits processive motion with a mean displacement that scales as t(0.32). In this work, we develop a model for segregation of chromosomal DNA as a Rouse polymer in a viscoelastic medium with a force applied to a single monomer. Our model demonstrates that the observed power-law scaling of the mean displacement and the behavior of the velocity autocorrelation function is captured by accounting for the relaxation of the polymer chain and the viscoelastic environment. We show that the ratio of the mean displacement to the variance of the displacement during segregation events is a critical metric that eliminates the compounding effects of polymer and medium dynamics and provides the segregation force. We calculate the force of oriC segregation in E. coli to be ∼0.49 pN.
大肠杆菌将其染色体拷贝分离以分配到子细胞中的物理机制尚不清楚，部分原因是难以解释分离过程中复杂的动态行为。对大肠杆菌先前染色体分离测量的分析表明，复制起点表现出持续运动，其平均位移与t(0.32)成比例。在这项工作中，我们建立了一个模型，将染色体DNA视为粘弹性介质中的Rouse聚合物，并对单个单体施加力来进行分离。我们的模型表明，通过考虑聚合物链的弛豫和粘弹性环境，可以捕捉到观察到的平均位移的幂律缩放以及速度自相关函数的行为。我们表明，分离事件中平均位移与位移方差的比值是一个关键指标，它消除了聚合物和介质动力学的复合效应，并提供了分离力。我们计算出大肠杆菌中oriC分离的力约为0.49皮牛。
