Bacterial Gene Transfer: Transduction, Transformation, Proof

Transduction is the process by which genetic material is transferred from one bacterium to another through a third party, which is a virus.

Temperate Phage: Following infection, a phage virus can either destroy its host cell or establish a stable association with the host cell, known as a prophage. The prophage is a nonpathogenic form of the virus that is maintained within the bacterium. Bacterial strains that are capable of producing and maintaining a prophage are called lysogenic, while host cells that are destroyed by virulent phage are called lytic.

Transduction 

During transduction, a phage virus infects a donor lytic bacterium, reproduces inside the bacterium, and then causes lysis (breaking) of the bacterium, releasing the virus along with the genetic material of the host. The integration of phage DNA and donor bacterial DNA occurs, resulting in the formation of a transducing particle. This particle can then infect another bacterium, which becomes a recipient. The recipient bacteria are lysogenic, and the genetic material of the donor and the phage is released inside the recipient. The recipient bacterium now contains three types of genetic material: DNA of the donor, DNA of the phage, and its own DNA.

 

The recipient bacterium undergoes division and DNA replication, followed by integration of the donor and recipient DNA. This results in the production of two types of bacteria: one that resembles the recipient bacteria, and another that exhibits characteristics of both the donor and the recipient. These bacteria are known as transduced bacteria and provide evidence of genetic recombination.

 

Transformation is the simplest form of bacterial gene transfer, involving the absorption of DNA into a cell, resulting in the transformation of the cell into a new type called transformed cells. Bacterial cells that release DNA fragments into their environment are called donor cells. If a released DNA fragment encounters a bacterium capable of transformation, it may be bound to the recipient and taken inside. Experiments by Fred Griffith in 1928 using Pneumococcus bacteria showed that transformation could occur in culture media, and later experiments by Dr. Oswald T. Avery and his team identified DNA as the transforming principle. This discovery in 1944 was a pivotal moment in the history of biology, demonstrating that DNA is the genetic material in cells.