frequently than with CIDs of a neighboring macrodomain or with genomic loci outside of that macrodomain. The Hi-C data showed that the E. coli chromosome was partitioning into two distinct domains. The region surrounding ter formed an insulated domain that overlapped with the previously identified Ter MD. DNA-DNA contacts in this domain occurred only in the range of up to ~280 kb. The rest of the chromosome formed a single domain whose genomic loci exhibited contacts in the range of >280-kb. While most of the contacts in this domain were restricted to a maximum distance of ~500 kb, there were two loose regions whose genomic loci formed contacts at even greater distances (up to ~1 Mb). These loose regions corresponded to the previously identified flexible and less-structured regions (NS). The boundaries of the insulated domain encompassing ter and the two loose regions identified by the Hi-C method segmented the entire chromosome into six regions that correspond with the four MDs and two NS regions defined by recombination-based assays. Proteins that drive macrodomain formation MatP A search for protein(s) responsible for macrodomain formation led to identification of Macrodomain Ter protein (MatP). MatP almost exclusively binds in the Ter MD by recognizing a 13-bp motif called the macrodomain ter sequence (matS). There are 23 matS sites present in the Ter domain, on average there is one site every 35-kb. Further evidence of MatP binding in the Ter domain comes from fluorescence imaging of MatP. Discrete MatP foci were observed that co-localized with Ter domain DNA markers. A strong enrichment of ChIP-Seq signal in the Ter MD also corroborates the preferential binding of MatP to this domain. MatP condenses DNA in the Ter domain because the lack of MatP increased the distance between two fluorescent DNA markers located 100-kb apart in the Ter domain. Furthermore, MatP is a critical player in insulating the Ter domain from the rest of the chromosome. It promotes DNA-DNA contacts within the Ter domain but prevents contacts between the DNA loci of Ter domain and those of flanking regions. How does MatP condense DNA and promote DNA-DNA contacts? The experimental results are conflicting. MatP can form a DNA loop between two matS sites in vitro and its DNA looping activity depends on MatP tetramerization. Tetramerization occurs via coiled-coil interactions between two MatP molecules bound to DNA. One obvious model based on in vitro results is that MatP promotes