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Physics Colloquium

How Life Shapes Time

Srividya Iyer-Biswas

Assistant Professor of Physics and Astronomy

Department of Physics

Purdue University, West Lafayette, IN

Abstract:

What are the quantitative laws governing the stochastic growth and division of individual cells? While great strides have been made in unravelling and modeling the details of the gene regulatory networks which dictate growth and division for different organisms, there is a regrettable paucity of quantitative physical laws derived from the complementary “top down” perspective. Introducing the unique combination of technologies that facilitated probing stochastic cellular dynamics with unprecedented precision, I will first summarize the “scaling laws” that govern fluctuations in growth and division of individual cells under steady-state growth conditions. Taking a minimalist perspective, I will argue for how these scaling laws reveal an elegant physical principle governing these complex biological processes: a single cellular unit of time, which scales with external conditions, governs stochastic dynamics of cell growth and division at a given condition. I will then focus on applications of the technology to probe more complex growth conditions, the corresponding generalizations of the physical principle, and the implications for the underlying biological systems design. Finally, I propose an integrative perspective of microbial growth dynamics under balanced conditions, by introducing a multi-scale theoretical framework that takes observables at both scales, single-cell and population, into account. Time permitting, I will make connections with stochasticintergenerational homeostasis of bacterial growth and form.