Structure of Bacterial Chromosome:
The genetic information of the prokaryotic cells is carried in the nucleoplasm on the structure termed bacterial chromosome. It consists of a double helical DNA (Deoxyribonucleic Acid) molecule, never associated with basic proteins, and has been shown in some prokaryotic to be circular. The bacterial chromosome is consequently not structurally homologous with the nuclear chromosomes of the eukaryotic cell, but rather with the organellar DNA present in the eukaryotic mitochondria and chloroplasts. It is probable that a single bacterial chromosome carries all the genetic information necessary to specify the essential properties of the prokaryotic cell.
Many bacteria can also harbor small extrachromosomal circular DNA molecules capable of autonomous replication, which are known as plasmids. So far investigated carry the determinants for such phenotypic characters and resistance to drugs and other antibacterial substances and for the enzymes which mediate certain metabolic pathways. The amount of DNA in a plasmid is from 0.1 to 5% of that in the bacterial chromosome.