BACTERIAL CHROMOSOMES AND PLASMIDS
bacterial chromosome
Bacteria usually have a single circular chromosome made of DNA. The bacterial chromosome is found in the bacterial cytoplasm and takes up approximately one third of the total volume of the bacterium. Bacterial DNA is about 1,000 times the length of the bacterium so how does the bacterium fit the DNA inside the bacterial cell? Bacterial DNA is super-coiled via an enzyme called DNA gyrase.
plasmids
Some bacteria (especially Gram Negative bacteria) have a plasmid in addition to the bacterial chromosome. A plasmid is a separate small, circular loop of DNA that carries non-essential information (drug resistance, pili production, toxin production). Plasmids replicate independently of the bacterial chromosome.
