What is nucleoid?
The nuclear region in a bacterial cell is called nucleoid. The nucleoid comprises a single long circular molecule of double stranded DNA also referred to as bacterial chromosome. There is, however, no nuclear membrane like in eucaryotic cells and it also lacks histones. In addition to a chromosome bacteria also contains small circular double stranded (extrachromosomal)
DNA molecules known as plasmids.
The plasmids may contain 5 to 100 genes and the bacteria can survive with and without them. The genes carried by plasmids are known to be responsible for antibiotic resistance, tolerance to toxic metals, production of toxic substances, and synthesis of certain enzymes. The plasmid DNA is used for genetic manipulations in biotechnological targets.