Understanding Bacterial Conjugation Process

Apr 3, 2025

Bacterial Conjugation

Overview

  • Bacterial Conjugation: A process of genetic transfer between bacterial cells requiring direct cell-to-cell contact.
  • Species Capability: While not all bacterial species can conjugate, many do. Conjugation can occur within the same species or between different species.

Key Components

  • F Factor (Fertility Factor):
    • A small DNA circle or plasmid essential for conjugation.
    • Bacteria containing the F factor are termed F+ (F plus).
    • Bacteria lacking the F factor are termed F- (F minus).

Process of Conjugation

  1. Pilus Formation:

    • An F+ cell or donor produces a structure called the pilus to connect with a recipient cell (F-).
  2. Initiation of Transfer:

    • The F factor is cut at the origin of transfer by the relaxosome, a protein assembly.
    • The relaxosome associates with the strand to be transferred, known as the T-DNA strand.
  3. Relaxosome Function:

    • Accessory proteins of the relaxosome are released, but a portion, called the relaxase, remains attached to the T-DNA.
  4. Transfer Mediation:

    • The T-DNA-relaxase complex is recognized by a coupling factor.
    • The complex is transferred to the exporter, a part of the F+ cell that is contiguous with the pilus.
  5. DNA Transfer:

    • The exporter pumps the T-DNA-relaxase complex into the recipient cell.
    • Once transferred, relaxase joins the ends to form a circular DNA in the recipient cell.
  6. Replication:

    • As the T-DNA is transferred, it is replicated to become double-stranded in the recipient cell.
    • In the donor cell, F factor DNA is also replicated and becomes double-stranded as the T-DNA is transferred.
  7. Completion:

    • At the end of the process, both cells have a complete double-stranded copy of the F factor.
    • The connection through the pilus is released, resulting in both cells being F+ and capable of further conjugation.