Exponential growth and metabolic dynamics in biophysical systems

Wei-Hsiang Lin^1*, Christine Jacobs-Wagner²

¹Academia Sinica, Institute of Molecular Biology, Taipei, Taiwan
²Department of Biology, Stanford University, California, USA

* Presenter:Wei-Hsiang Lin, email:whl243@gate.sinica.edu.tw

Biophysical systems, which are capable to grow and respond to environmental change, are typically nonlinear and non-equilibrium. The principles for how these systems control their energy, material fluxes and maintain their stability are largely open in physics. I will present two research projects in this talk:

(i) Single-cell measurements of ATP dynamics: ATP (adenosine triphosphate) is the common energy carrier for all living systems and is essential for cell metabolism and RNA synthesis. Using microfluidic cell culture with ATP fluorescence biosensor, I measured the long-term ATP dynamics for E. coli cells for multiple days. I found that intracellular ATP level is coupled with bacterial cell cycle, and the ATP oscillation is attenuated in the absence of overflow metabolism. I also found that ATP homeostasis is correlated with single-cell growth, where cell cycles with smaller ATP fluctuation grow and divide faster on average.

(ii) Theoretical frameworks for exponential growth: physical systems with different scaling laws grow at different modes. Biophysical systems (such as cells and ecosystems) often exhibit exponential growth in the long-term, while the underlying scaling property have not been described. I will discuss how nonlinear scaling of reaction fluxes is related with exponential growth. In addition, I will discuss a new way to analyze biomass fluxes in reaction network with delay differential equations, which enables us to calculate exponential growth rate in frequency domain.

Keywords: exponential growth , ATP, fluorescent biosensor, microfluidics, oscillatory dynamics