Bacterial genetics: Mechanism of Generalized transduction

In Transduction, DNA is transferred from one cell to another through the agency of viruses.  Genetic transfer of host gene by bacteriophage occurs in two ways-Generalized transduction and specialized transduction.

In generalized transduction, virtually any genetic marker can be transferred from donor to recipient cell but it occurs at a low frequency.

To understand the process of generalized transduction, you must first be aware about lytic cycle of Bacteriophage.

When a population of a sensitive bacterium is infected with bacterioophage following sequential events occurs:

  1. Attachment/Adsorption of bacteriophage to the bacteria
  2. Penetration of phage DNA
  3. Replication of phage DNA/RNA
  4. Synthesis of nucleic acid and proteins
  5. Assembly of phage protein and nucleic acid
  6. Release of mature bacteriophage

The above mentioned process is the normal process, but in some occasion, enzyme responsible for packaging viral DNA into the bacteriophage accidently package host DNA.

When the bacterial cell is lysed, these transducing (host DNA within phage coat) particles are released along with normal virions.  These defective transducing particles cannot initiate the normal viral infection as they do not contain viral DNA (instead they have host DNA).

When the lysate containing both normal virions and tranducing phage particle are mixed with sensitive bacterial population,  most of the bacteria get infected with normal virions and very few bacteria receives DNA of the previous host bacterium.

This DNA now undergoes genetic recombination with the DNA of the new host. If the donor genes do not undergo homologous recombination with the recipient bacterial chromosome, they will be lost.

Bacteriophages that form transducing particles can be either temperate or virulent.

Transduction has been found to occur in a variety of bacterial populations including:

  1. Escherichia coli
  2. Pseudomonas spp
  3. Salmonella spp
  4. Staphylococcus spp

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