Evolving Cell Size Control (close to criticality ?)

Cells can control their own sizes. While it is clearly necessary for homeostatis, it is rather fascinating to think that evolution came out with specific biochemistry for cells to essentially measure themselves. Many models have been proposed, but in that paper, in collaboration with the Skotheim group at Stanford, we tried to ask the inverse question : what kind of cell size control mechanisms can evolve, and most importantly why ? We used our very own evolutionary algorithm, phi-evo, to study this problem and derive biochemical networks performing cell size control. We find many cool results, in particular many different solutions depending on evolutionary pressure. My favourite one is a crazy system where small cells can become super big because of stochastic fluctuations, before going through multiple divisions to come back to smaller sizes, closing a cycle of growth/degrowth where cell size is controlled only on average ! Even more fascinating : it turns out this process is close to actual cell control mechanisms such as the one in Chlamydomonas, and from a more fundamental and physical standpoint, it presents signatures of self-organized criticality in complex systems (think of avalanche !)

A crazy cell cycle control : when cells are small, stochastic fluctuations are more probable, and trigger huge growth. From there, cells go through multiple cycles until they get small again !