Résumé
Biology offers new systems for Physics, namely proteins and molecular motors in interaction with biopolymers like DNA and messenger RNA. This field is at the interface between active matter, polymer physics, and physics of colloids. Interestingly, cells also need to increase locally concentrations of proteins in a phase transition-like mechanism to realize vital function like cell division, DNA repair, DNA segregation etc. During this HDR defense, I will offer a physical perspective of intracellular phase transition with the example of bacterial DNA segregation. I will also discuss the motion of ribosomes along messenger RNA, an example of unidimensional inhomogeneous transport giving rise to different dynamical regimes.