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6.2.2.2.5. Bacterial DNA

Bacterial chromosome. Bacterial genetic material

The bacterial chromosome is made up of a single circular double-stranded DNA molecule, associated with non-histone proteins. It is not surrounded by any nuclear membrane, so the region in which it is located is called a nucleoid. It is usually attached to the mesosomes.

Bacterial DNA has the function of maintaining and preserving genetic information and directing the functioning of all bacterial metabolism.

As a peculiarity, many bacteria have plasmids, small rings of DNA, which are independent of the chromosome and which can be duplicated. The following stand out:

  • Plasmid or factor F: allows the cell to have the ability of conjugation.
  • R plasmids: their genes encode enzymes that provide resistance against antibiotics. These genes are passed from stem cells to daughters, but they can also be transferred to the bacterial chromosome, viruses, and other bacteria. This is the reason why diseases that were controlled, such as tuberculosis, can resurface.

The plasmids are small molecules of double - stranded circular DNA that are present in many bacteria. They are not part of the bacterium's chromosome and can duplicate, also independently.

Fundamental ideas about bacterial chromosome and plasmids

Bacteria have only one chromosome (circular double-stranded DNA) that contains all the genetic information of the cell.

In addition to the bacterial chromosome, many bacteria have other smaller DNA molecules, also circular, called plasmids, with non-essential genetic information but which can be very advantageous for adaptation to the environment in which they live, such as plasmids that provide them antibiotic resistance.