细菌细胞周期的准确调控对维持其生存，保持正常的生长分裂状态至关重要。但是，细菌是如何做到细胞周期的精确调控，至今不明。申请人的前期研究发现，在高生长速率条件下，细胞大小与细胞生长速率和DNA复制起始到对应细胞分裂的时间间隔两者的乘积呈指数关系，验证了前人提出的“S-M-K生长法则”。然而，在低生长速率条件下，该法则是否还适用，是领域内尚未解决的问题。针对该关键科学问题，申请人拟通过显微观测、定量PCR、流式细胞检测、微流控和单细胞实时成像等研究手段，利用合成生物学技术线性改变细胞大小，对低生长速率条件下的细胞周期进行系统研究。本项目的开展将深化人们对细菌细胞周期的理解，为研究细菌细胞周期调控的分子机制提供重要线索。

Bacteria cell cycle should be tightly regulated in order to maintain the normal growth and division of the cell. But, by which mechanisms the cells can tightly control their cell cycle are still unknown. We have found that, under fast growth conditions, the average cell volume scales exponentially with growth rate, with a scaling exponent equal to the time from initiation of a round of DNA replication to the cell division at which the corresponding sister chromosomes segregate, which validates the Schaechter-Maaløe-Kjeldgaard Growth Law. However, under slow growth conditions, how the cell cycle operates are still unknown. In this study, we are going to characterize the cell cycle of Escherichia coli under slow growth conditions by using microscope observation, quantitative PCR, flow cytometeric and single cell tracking technologies. Knowledge gained here will deepen our understanding of the bacterial cell cycle and provide important clues for studying molecular mechanisms of the bacterial cell cycle.