The Escherichia coli nucleoid exists in a liquid-liquid phase separated state which seems to be responsive and tunable towards stresses

Abstract

The E. coli chromosome’s (1,000-fold) compaction into the non-membrane-bound compartment called the nucleoid has remained a mystery. For several decades, predictions have existed that the nucleoid is phase separated, with macromolecular crowding playing a major role in DNA compaction. Here, we present evidence for 1) The dynamic nature of the nucleoid; 2) LLPS shown by a major log-phase non-sequence specific Nucleoid Associated Protein (NAP), under physiological conditions; 3) the potency of the NAP to phase separate with DNA (all possible conformations) and RNA; 4) the tunable nature of this phase separation, based on the relative amounts of protein homologs ; 5) Phase separation of another NAP, a stationary phase protein; and 6) Coacervation of two proteins in LLPS condensates, which could be relevant to the well-known crystallization potency of stationary phase NAP (a DNA protection mechanism) in cells.