Plasmid Transfer and Conjugation

Donor and Recipient Cell Interaction

• Plasmids are small DNA fragments separate from the main chromosome.
• They carry genetic information, such as antibiotic resistance.

Initial Contact

• The initial step in plasmid transfer involves contact between the donor and recipient cells.
• Pili of the donor cell recognize and bind to specific receptor sites on the cell wall of the recipient cell.

Plasmid Mobilization

• The plasmid becomes mobile for transfer.
• An enzyme cleaves one strand of the plasmid at a specific nucleotide sequence.
• This sequence is called the origin of transfer.

DNA Transfer

• A single strand of the plasmid, starting at the origin of transfer, enters the recipient cell.

Synthesis of Complementary Strand

• Once inside the recipient cell, a complementary strand to the transferred DNA is synthesized.

Cell Conversion

• When donor and recipient cells are mixed, all cells eventually behave like donors.

Conjugation Defined

• Conjugation is a gene transfer mechanism requiring direct contact between donor and recipient cells.

Detailed Steps of Plasmid Transfer

• A plasmid is a small piece of DNA, separate from the main chromosome, carrying genetic information (e.g., antibiotic resistance).
• The first step is contact between donor and recipient cells.
• Pili from the donor cell recognize and bind to specific receptor sites on the recipient cell wall.
• The plasmid is then mobilized for transfer.
• An enzyme cleaves one strand of the plasmid at a specific nucleotide sequence called the origin of transfer.

Recipient Cell Integration

• A single strand of the plasmid, beginning at the origin of transfer, enters the recipient cell.
• Inside the recipient cell, a complementary strand to the single DNA strand is synthesized.
• When donor and recipient cells are mixed, eventually all cells behave like donors.