Transduction in Bacteria

Transduction is the mechanism of genetic exchange or reproduction described by Zinder and Lederberg in 1952 pertaining to certain bacteria, specifically those responsible for causing mouse typhoid, such as Salmonella typhimurium.

The transfer of bacterial DNA from a donor cell to a recipient cell with the assistance of a bacteriophage is referred to as bacteriophage-mediated genetic material transfer. This process, known as transduction, has been observed in various bacterial species, including E. coli, Proteus, Schizella, and Staphylococcus.

1.0Steps of Transduction in Bacteria

2.0Types of Transduction

Transduction is generally of two types : 

• Generalized transduction 
• Specialized transduction 

Generalized transduction 

Bacteriophage infection initiates a process facilitated by specific DNA segments called prophage particles in the bacterial cell's cytoplasm. In the course of a lysogenic bacterial cell's infection, bacterial DNA fragments while the bacteriophage's nucleic acid utilizes bacterial enzymes for new phage component synthesis. 

Simultaneously, these developing phage particles integrate the bacterial DNA fragments into their genetic material.  Later, these progeny phage particles transfer the bacterial cell's genetic material to newly infected bacterial cells, illustrating the process of generalized transduction where bacteriophages actively aid in the transfer of bacterial DNA fragments. Example ; The best known generalized transducing phages are P22 in S. typhimurium and P1 in E. coli.

Specialized transduction

As discovered by Andre Lwoff et al. in 1953, is a phenomenon where certain bacterial strains can endure extended periods of bacteriophage infection without bacterial cell lysis. In these lysogenic bacteria, the bacterial DNA joins with the phage DNA and replicates together. This state is maintained by a repressor protein that inhibits phage particle synthesis. When this protein production ceases, the bacterial cell begins to produce phage components.

Before phage particle synthesis initiates, both phage and bacterial DNA degrade, and some bacterial genes are incorporated into the phage DNA, replicating alongside it. The progeny phage particles differ from their parent phage. When they infect new bacterial cells, they transmit closely linked bacterial genes. This specialized transduction transfers specific genes closely associated with the phage DNA. 

Example ; Bacteriophage lambda (𝛌) is the best-known specialized transducing phage; 𝞴 carries only the gal (required for the utilization of galactose as an energy source) and bio (essential for the synthesis of biotin) genes from one E. coli cell to another.

3.0Significance of Transduction

Transduction in bacterial genetics is crucial for various reasons:

Gene Exchange: It helps bacteria diversify their genetic makeup, potentially gaining new abilities like antibiotic resistance by swapping genes through bacteriophages.

Gene Therapy and Engineering: Bacteriophage-derived vectors are used to deliver therapeutic genes, aiding in treating genetic disorders and advancing genetic engineering.

Research Tool: It is vital for understanding how genes function, are expressed, and transferred within bacteria.

Evolutionary Influence: Transduction shapes bacterial evolution by introducing new genetic material, impacting their ability to adapt and their ecological roles.

Biotechnological Use: It's instrumental in creating GMOs and producing specific proteins, such as insulin or vaccines, with applications across fields like medicine and agriculture.