Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

29-POS Board 15 Interrogating the Bacterial Cell Cycle by Cell Dimension Perturbations and Stochastic Modeling Hai Zheng 1,2 , Po-Yi Ho 3 , Meiling Jiang 1 , Bin Tang 4 , Weirong Liu 1,2 , Dengjin Li 1 , Xuefeng Yu 5 , Nancy Kleckner 6 , Ariel Amir 3 , Chenli Liu 1,2 . 3 Harvard University, Cambridge, MA, USA, 1 Shenzhen Institutes of Advanced Technology, Shenzhen, China, 2 University of Chinese Academy of Sciences, Beijing, China, 4 Southern University of Science and Technology, Shenzhen, China, 5 Shenzhen Institutes of Advanced Technology, Shenzhen, China, 6 Harvard University, Cambridge, MA, USA. Bacteria tightly regulate and coordinate the various events in their cell cycles to duplicate themselves accurately and to control their cell sizes. Growth of Escherichia coli , in particular, follows Schaechter’s growth law. The law says that 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. Here, we test the robustness of the growth law to systematic perturbations in cell dimensions achieved by varying the expression levels of mreB and ftsZ. We found that decreased mreB levels resulted in increased cell width, with little change in cell length, whereas decreased ftsZ levels resulted in increased cell length. In both cases, the time from replication termination to cell division increased with the perturbed dimension. Importantly, the growth law remained valid over a range of growth conditions and dimension perturbations. The growth law can be quantitatively interpreted as a consequence of a tight coupling of cell division to replication initiation. Its robustness to perturbations in cell dimensions strongly supports models in which the timing of replication initiation governs that of cell division, and cell volume is the key phenomenological variable governing the timing of replication initiation. These conclusions are discussed in the context of our recently proposed “adder-per-origin” model, in which cells add a constant volume per origin between initiations and divide a constant time after initiation.

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