The E. coli chromosome is a single circular chromosome, situated within the cytoplasm. Consisting of transcriptional units made of operons and genes, the chromosome is able to produce both monocistronic and polycistronic transcripts. Transcriptional units are generally orientated in the same direction, preventing polymerase crashes.
The chromosome has few introns, as is characteristic of prokaryotes, with the DNA mainly coding for proteins and functional RNAs.
Nucleoid associated proteins (NAPs) are able to induce bends in the DNA. This allows the DNA to be packed more tightly, with HU being highly conserved across many species.
Supercoiling, by topoisomerase, also helps to condense the DNA. This twisting of the DNA can also be used to change the transcriptional activity of chromosomal regions. The prevalence of positive and negative supercoils can be modulated by the presence of topoisomerases I, II, III, and IV.
All transcriptional units are made up of a promoter, polymerase binding site (Shine-Dalgarno sequence), START codon, gene(s), STOP codon, and terminator. Different types of promoters can be used to control the expression levels of transcriptional units in response to molecules and other stimulants.