Generalized transduction and specialized transduction are two mechanisms by which bacterial DNA can be transferred between cells through bacteriophages (viruses that infect bacteria). While both processes involve the transfer of DNA, they differ in the types of DNA they can transfer and the mechanisms by which they do so.
1. Generalized transduction:
- Generalized transduction can transfer any random fragment of bacterial DNA from the donor cell to the recipient cell.
- It occurs when a bacteriophage mistakenly packages a fragment of the host bacterium's DNA instead of its own viral DNA during the assembly of new phage particles.
- This mistake can happen due to errors in the packaging process, resulting in the encapsulation of bacterial DNA instead of viral DNA.
- When the infected bacteriophage carrying the bacterial DNA infects another bacterium, it injects the bacterial DNA into the recipient cell.
- The transferred DNA can integrate into the recipient cell's genome through recombination or have other effects on the recipient cell's physiology.
- Generalized transduction is considered an accidental and rare event, and it can occur in various bacterial species.
2. Specialized transduction:
- Specialized transduction transfers specific and limited portions of bacterial DNA that are located near the integration site of a temperate bacteriophage (a bacteriophage that can enter a lytic or lysogenic cycle).
- It occurs when a temperate bacteriophage enters the lysogenic cycle by integrating its DNA into the host bacterium's genome.
- During the excision process of the bacteriophage from the host genome to enter the lytic cycle, adjacent bacterial DNA flanking the phage DNA may be mistakenly excised along with it.
- This results in the transfer of both phage DNA and specific adjacent bacterial DNA into the recipient cell when the infected bacteriophage lyses the donor cell and releases new phage particles.
- The transferred bacterial DNA can potentially recombine with the recipient cell's genome, leading to the acquisition of new genetic traits.
- Specialized transduction is a specific and controlled process that occurs only in temperate bacteriophages and specific bacterial strains.
In summary, generalized transduction transfers random fragments of bacterial DNA, while specialized transduction transfers specific and limited portions of bacterial DNA located near the integration site of a temperate bacteriophage. Generalized transduction is an accidental process, whereas specialized transduction is a specific and controlled mechanism associated with temperate bacteriophages.