Scale invariance of bacterial cell size fluctuations during starvation

In stable environments, cell size fluctuations have been reported to show simple statistical properties. For instance, the cell size distribution of various species of eukaryotes is expressed by a common function, which is scaled by the mean body size of the species [1]. However, the typical body size is easily affected by environmental changes, e.g., the bacterial cell size drastically decreases in response to nutrient starvation.
Here, by developing a microfluidic device that realizes a uniform and switchable environment for dense bacterial populations, we observe the morphological response of growing E. coli cells against abrupt starvation [2]. While the typical cell size continuously decreases, we find that the cell size distributions rescaled by the mean body size at each time is kept unchanged and determined by the growth condition before starvation. Our observations are underpinned by a model based on cell growth and cell cycle. Further, we numerically determine the range of validity of the scale invariance over various timescales of the starvation process, revealing that the state of cell cycle is crucial for the scale invariance.

[1] A Giometto et al., PNAS 110, 4646 (2013)
[2] T. Shimaya, R. Okura, Y. Wakamoto, and Kazumasa A. Takeuchi, arXiv:2004.04903