Prokaryotic chromosomes:

The DNA of a bacterial cell, like as Escherichia coli is a circular double-stranded molecule frequently referred  to as the bacterial  chromosome. The circular DNA is packaged into a region of the cell known as the nucleoid where it is organized  into 50 or so loops  or domains  which are bound  to a central  protein scaffold  attached to the cell membrane. Above figure illustrates these industries, although only six loops are shown for clarity. Within this structure the DNA is in fact not a circular double-stranded  DNA molecule like  as that shown  in fig.1b but is negatively supercoiled, which is, it is twisted upon itself and is also  complexed  with various DNA-binding proteins,  the  most  common  of that are proteins HU, H-NS and HLP-1. These are histone-like proteins.

figure:  (a) The association of circular bacterial DNA with a protein scaffold; (b) a circular double-stranded DNA molecule; (c) supercoiled DNA.