The E. coli chromosome is represented by the blue lines folded in loops, the oriC by a black square, and the RNA Pol molecules by green circles. For simplicity, only one of the prominent RNA Pol foci and the replisome are shown. RNA Pol foci at the clustering of rrn (red), resembling a bacterial nucleolus, are spatially organized at the periphery of the nucleoid for compartmentalization. Foci of NusA and NusB co-localize with RNA Pol foci, indicating that RNA Pol foci are transcription factories for the coupling of rRNA synthesis and ribosome biogenesis including processing of the pre-rRNA. Long-distance interactions of DNA loops are indicated. Compartmentalization of the replisome is also shown, but the two major cellular functions of transcription and replication are largely spatially segregated. Modified from (Jin et al., 2015).