Non Equilibrium Transitions in a Template Copying Ensemble - Arthur Genthon (MPIPKS, Dresde, Germany)

Part 1: Non Equilibrium Transitions in a Template Copying Ensemble. The fuel-driven process of replication in living systems generates distributions of copied entities with varying degrees of copying accuracy. Here we introduce a thermodynamically consistent ensemble for investigating universal population features of template copying systems. In the context of copolymer copying, coarse-graining over molecular details, we establish a phase diagram of copying accuracy. We discover sharp non-equilibrium transitions between populations of random and accurate copies. Maintaining a population of accurate copies requires a minimum energy expenditure that depends on the configurational entropy of copolymer sequences.

Part 2: Bridging the gap between stochastic single-cell behavior and population growth. In steady-state, cell populations grow exponentialy with a deterministic rate, also called Malthus parameter or population fitness, in spite of the highly stochastic nature of the cell cycle. Here we derive equations which link the population growth rate to various sources of noise at the single cell level: in volume partitioning at division, elongation rate, and target division size in the context of cell size control. This allows for a comparison of the mechanisms of cell size regulation to maximize the population fitness. We also observe that the statistical characterization of cell size control in freely growing populations is biased compared to single-lineage (mother machine) experiments, questioning the relevant scale to discuss size regulation.

Contact: Natale Scaramozzino