Cytoplasmic Dynamics Reveals Two Modes of Nucleoid-Dependent Mobility
Cytoplasmic Dynamics Reveals Two Modes of Nucleoid-Dependent Mobility
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DOI：
10.1016/j.bpj.2014.10.030
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发表时间：
2014-12-02
影响因子：
3.4
通讯作者：
Wiggins, Paul A.
中科院分区：
文献类型：
--
作者：
Stylianidou, Stella;Kuwada, Nathan J.;Wiggins, Paul A.
有人提出，由于细菌类核中大分子的物理排斥所产生的力在细菌细胞的组织中起着核心作用，但这一提议尚未得到定量测试。为了研究这一假设，我们通过对荧光标记异位MS2-mRNA复合物的数千个完整细胞周期轨迹的定量分析，绘制了细菌细胞质中大蛋白复合物的一般运动。我们发现这些复合物在细胞质中的运动强烈依赖于它们沿着细胞长轴的空间位置，并且它们的动力学与只需要类核排斥和膜约束的定量模型一致。该分析还表明，类核增加了MS2-mRNA复合物的迁移率，导致最低和最高类核密度区域之间的扩散系数增加了四倍。这些数据为两种类核作用模式提供了强有力的定量支持：一种是被广泛接受的在组织细胞过程中排除类核的机制，另一种是新提出的类核促进在细胞质中快速运动的模式。
It has been proposed that forces resulting from the physical exclusion of macromolecules from the bacterial nucleoid play a central role in organizing the bacterial cell, yet this proposal has not been quantitatively tested. To investigate this hypothesis, we mapped the generic motion of large protein complexes in the bacterial cytoplasm through quantitative analysis of thousands of complete cell-cycle trajectories of fluorescently tagged ectopic MS2-mRNA complexes. We find the motion of these complexes in the cytoplasm is strongly dependent on their spatial position along the long axis of the cell, and that their dynamics are consistent with a quantitative model that requires only nucleoid exclusion and membrane confinement. This analysis also reveals that the nucleoid increases the mobility of MS2-mRNA complexes, resulting in a fourfold increase in diffusion coefficients between regions of the lowest and highest nucleoid density. These data provide strong quantitative support for two modes of nucleoid action: the widely accepted mechanism of nucleoid exclusion in organizing the cell and a newly proposed mode, in which the nucleoid facilitates rapid motion throughout the cytoplasm.