CAREER: Cell Size and Cell Cycle Control in the Presence of Fluctuations in Bacteria

细菌的生长和细胞周期之间存在着一种微妙的定量关系。引人注目的是，DNA复制的开始被认为与特定细胞质量（临界质量）的实现相一致，这种现象与生长速度无关。这是20世纪50年代和60年代细菌生理学领域最重要的定量思想之一，它仍然是我们目前对细胞周期控制的理解的基础。然而，令人惊讶的是，我们还不了解分子水平调控如何控制生长和细胞周期之间的全局关系。为此，该项目将采用最先进的显微镜来可视化活细胞中的复制和细胞分裂机制，使我们能够精确测量细胞生长，DNA复制和细胞分裂时间。特别是，该项目将研究细胞如何在单细胞水平上对生理扰动作出反应。单细胞方法很重要，因为我们可以获得与细胞内波动相关的关键分子水平信息，而这些信息在群体水平的研究中不可避免地会丢失。重要的是，该项目将采用两种进化上不同的模式生物，大肠杆菌和枯草芽孢杆菌，使我们能够确定细胞周期调节的哪些方面可能广泛保守。在这样做的过程中，该项目将为细胞是否生长到临界细胞质量以启动特定细胞周期事件的基本问题提供明确的答案。这项研究的优势在于它能够弥合实验与理论之间的差距。除了上述实验部分外，理论部分还包括对所获得的数据进行定量建模，以进行实验可测试的预测。这项研究的结果将对我们对所有细胞生长的基本理解产生影响。更广泛的影响定量生物学不仅仅是给生物学家已经知道的东西增加数字。该方法的强大之处在于，它将物理科学的定量严谨性引入生物学中，以识别和解决重要而有趣的问题。作为加州大学圣地亚哥分校定量生物学新倡议的一部分，该项目旨在将定量生物学方法的文化从K12传播到圣地亚哥地区的研究生水平教育。这个综合项目非常强调本科阶段跨学科研究经验的重要性。为了激励学生和教育工作者，也为了激励公众，每年夏季将为圣地亚哥地区的本科生提供跨学科研究训练营，可能还有高中生。来自代表性不足的少数群体的学生将被特别鼓励参与，西班牙裔服务机构（圣地亚哥州立大学）将在该项目中合作。一位来自冷泉港实验室课程的前讲师加入了这个项目，设计并共同教授了包括分子生物学、定量显微镜、微流体学和图像分析在内的训练营模块。总体目标是设计典型的本科生研究模块，并将其整合到UCSD、SDSU和其他大学的定量生物学标准本科生研究课程中。这个奖项是由细胞动力学和功能以及生命系统物理学共同创立的。

Intellectual Merit An exquisite, quantitative relationship between growth and cell cycle exists in bacteria. Strikingly, the onset of DNA replication is assumed to coincide with achievement of a specific cell mass (critical mass), a phenomenon that is independent of growth rate. This was one of the most important quantitative ideas in the field of bacterial physiology during the 1950s and the 1960s, and it still serves as the foundation for our current understanding of cell cycle control. Surprisingly, however, we do not yet understand how the molecular-level regulation controls the global relationship between growth and cell cycle. To this end, this project will employ state-of-the-art microscopy to visualize replication and cell division machinery in living cells, allowing us to precisely measure cell growth, DNA replication and cell division timing. In particular, the project will study how the cell responds to physiological perturbations at the single-cell level. Single-cell approach is important, because we can acquire critical molecular-level information related to intracellular fluctuations that is inevitably lost in population-level studies. Importantly, this project will employ two evolutionarily divergent model organisms, Escherichia coli and Bacillus subtilis, permitting us to determine which aspects of cell cycle regulation are likely to be broadly conserved. In doing so, this project will provide a definitive answer to the fundamental question of whether or not cells grow to a critical cell mass to initiate a specific cell-cycle event. The strength of this research lies in its ability to bridge the gap between experiment and theory. In addition to the experimental component described above, the theory component involves quantitative modeling of the acquired data to make experimentally testable predictions. The outcome of the research will have implications for our fundamental understanding of the growth of all cells.Broader Impacts Quantitative biology is more than adding numbers to what biologists already know. The power of the approach is to bring quantitative rigor from physical sciences to identify and solve important and interesting problems in biology. As part of the new initiative of quantitative biology at the University of California at San Diego, the project aims to spread the culture of quantitative approaches to biology from K12 to graduate level education in the San Diego area. This integrative project places great emphasis on the importance of interdisciplinary research experiences at the undergraduate level. To inspire not only the students and educators but also the general public, an annual summer interdisciplinary research bootcamp will be offered for undergraduate students, and possibly senior high-school students, in the San Diego area. Students from under-represented minority groups will be particularly encouraged to participate, and a Hispanic Serving Institution (San Diego State University) will collaborate in the project. A former instructor from the Cold Spring Harbor Laboratory Courses joins the project to design and co-teach the bootcamp modules that incorporate molecular biology, quantitative microscopy, microfluidics, and image analysis. The overall goal is to design exemplary undergraduate research modules and integrate them into standard undergraduate research curricula in quantitative biology at UCSD, SDSU, and other universities. This award is cofounded by the programs in Cellular Dynamics and Function and the Physics of Living Systems.