English: Formation of the Escherichia coli nucleoid A. An illustration of an open conformation of the circular genome of Escherichia coli. Arrows represent bi-directional DNA replication. The genetic position of the origin of bi-directional DNA replication (oriC) and the site of chromosome decatenation (dif) in the replication termination region (ter) are marked. Colors represent specific segments of DNA as discussed in C. B. An illustration of a random coil form adopted by the pure circular DNA of Escherichia coli at thermal equilibrium without supercoils and additional stabilizing factors.[5][6] C. A cartoon of the chromosome of a newly born Escherichia coli cell. The genomic DNA is not only condensed by 1000-fold compared to its pure random coil form but is also spatially organized. oriC and dif are localized in the mid-cell, and specific regions of the DNA indicated by colors in A organize into spatially distinct domains. Six spatial domains have been identified in E. coli. Four domains (Ori, Ter, Left, and Right) are structured and two (NS-right and NS-left) are non-structured (See section 4 of the main text for details). The condensed and organized form of the DNA together with its associated proteins and RNAs is called nucleoid.