Plasmids are the genetic information, circular DNA strands to be precise, located in the cytoplasm of the cell with the potential to replicate independently. These plasmids are DNA delivering vectors. However, the DNA transfer is not a true exchange, as DNA(a small strand of the chromosome) is transferred to another cell and not exchanged. The role of prokaryotic plasmids is significant in the development of the bacterial genome and metabolic activities of the host cell.
This transfer can take place through one of these processes:
Transfer of DNA through direct cell-to-cell contact which is brought about by plasmids. Plasmids encode a mechanism to communicate the transfer from donor to recipient cell and are hence is unidirectional. Sex Pilus in gram-negative bacteria is a plasmid which attaches to the recipient and through a conjugal bridge transfers DNA.
Free fragments of DNA floating in a medium is picked up by the recipient cell for which the requisite is that recipient cells need to be competent.
Transfer of DNA from one to another bacterium through a bacteriophage(bacteria-infecting virus). DNA thus shared is protected by the bacteriophage, hence it is one of the most efficient means of transfer.
- Transposable elements
One of the ways of plasmid transfer is when DNA ‘jump’ within a genome from one to another position, inserting copies of themselves in new points, snipping and pasting themselves.
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