Plasmids are shared between bacteria through a process called conjugation. This is a type of horizontal gene transfer where a donor bacterium transfers a copy of its plasmid to a recipient bacterium. It involves physical contact between the two bacteria cells. Here's a breakdown of the conjugation process:
- Conjugation apparatus: The donor bacterium possesses a specialized structure called a conjugation pilus. This pilus acts like a bridge, connecting the donor and recipient cells.
- Plasmid transfer: A single strand of the plasmid DNA is replicated and transferred through the pilus to the recipient cell.
- Integration: Once inside the recipient cell, the plasmid DNA circularizes and replicates independently, becoming established in the new host.
Other mechanisms involved in the transfer of plasmid are:
Transformation
Bacteria can also acquire plasmids from the environment through a process called transformation. This involves the uptake of naked DNA molecules from dead bacteria or released by other bacteria in the surrounding environment.
Transduction
While this is not the primary way by which plasmids are shared. Some viruses (bacteriophages) can accidentally package plasmid DNA from a donor bacterium and transfer it to a recipient bacterium during infection.
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