Biopolymer organization upon confinement

Biopolymers in vivo are typically subject to spatial restrains, either as a result of the substantial molecular crowding of the cellular medium or by direct spatial confinement. The high level of packing of DNA encountered in all types of organisms provides a prototypical example of the ubiquity of biopolymer confinement and of the several accompanying physical issues: How can the high level of packing be compatible with the necessity to access and process the genomic material? By which mechanisms it is avoided the eccessive geometrical and topological entanglement of dense phases of biopolymers? These and other fundamental questions have been addressed in recent years by both experimental and theoretical means. A review of the salient results, particularly those obtained by numerical studies, is presented here. The review is mostly devoted to DNA packaging inside bacteriophages, which is the best studied example both experimentally and theoretically. Recent selected biophysical studies of the bacterial genome and of chromosome segregation in eukaryotes are also covered.