School of Life Sciences, Swiss Federal Institute of Technology in Lausanne (EPFL), Lausanne 1015, Switzerland.
Nat Commun. 2013;4:2470. doi: 10.1038/ncomms3470.
During the bacterial cell cycle, chromosome replication and cell division must be coordinated with overall cell growth in order to maintain the correct ploidy and cell size. The spatial and temporal coordination of these processes in mycobacteria is not understood. Here we use microfluidics and time-lapse fluorescence microscopy to measure the dynamics of cell growth, division and chromosome replication in single cells of Mycobacterium smegmatis. We find that single-cell growth is size-dependent (large cells grow faster than small cells), which implicates a size-control mechanism in cell-size homoeostasis. Asymmetric division of mother cells gives rise to unequally sized sibling cells that grow at different velocities but show no differential sensitivity to antibiotics. Individual cells are restricted to one round of chromosome replication per cell division cycle, although replication usually initiates in the mother cell before cytokinesis and terminates in the daughter cells after cytokinesis. These studies reveal important differences between cell cycle organization in mycobacteria compared with better-studied model organisms.
在细菌细胞周期中，为了维持正确的倍性和细胞大小，染色体复制和细胞分裂必须与整体细胞生长相协调。分枝杆菌中这些过程的时空协调尚不清楚。在这里，我们使用微流控技术和延时荧光显微镜来测量分枝杆菌单个细胞中细胞生长、分裂和染色体复制的动力学。我们发现，单细胞生长是大小依赖性的（大细胞比小细胞生长得更快），这暗示了细胞大小稳态中的大小控制机制。母细胞的不对称分裂产生大小不等的姐妹细胞，它们以不同的速度生长，但对抗生素没有差异敏感性。尽管复制通常在胞质分裂前在母细胞中开始，并在胞质分裂后在子细胞中结束，但每个细胞在每个细胞分裂周期中仅限制进行一轮染色体复制。这些研究揭示了分枝杆菌细胞周期组织与研究更为充分的模式生物之间的重要差异。
