Bacterial Transduction Definition, Principle, Steps, Examples

Bacterial Transduction: Definition, Principle, Steps, Examples

Bacitracin Susceptibility The test is a microbiological technique designed to separate beta-hemolytic streptococci, namely Streptococcus pyogenes (Group A Streptococcus) from other streptococcal species. The test is based on bacteria’s sensitivity to the antibiotic bacitracin.

What is Bacterial Transduction?

Bacterial transduction is a type of horizontal gene transfer in which bacteriophages, or viruses that infect bacteria, transport genetic material from one bacterial cell to another. This transfer of genetic material might cause genetic recombination in the receiving bacterial cell, resulting in new genetic characteristics. Transduction is important for bacterial evolution, adaptability, and the spread of antibiotic resistance.

Principle of Bacterial Transduction

Generalized Transduction

During generalized transduction, any piece of the donor bacterium’s DNA may be mistakenly packaged into a phage particle. This normally happens during a bacteriophage’s lytic cycle, when the virus hijacks the bacterial machinery and produces new phage particles.

Mechanism

Phage Infection: A bacteriophage infects a donor bacterial cell and inserts its DNA into the host.
Bacterial DNA Degradation: Phage DNA takes over the host machinery, causing bacterial DNA to disintegrate.
Phage Assembly: During the assembly of new phage particles, bacterial DNA fragments may be packed into phage capsids rather than phage DNA.
The bacterial cell lyses, releasing newly produced phages, including ones containing bacterial DNA.
Infection of Recipient Bacterium: A phage with bacterial DNA infects a fresh recipient bacterial cell and injects the donor’s bacterial DNA.
Recombination: The transferred bacterial DNA recombines with the recipient’s genome, possibly introducing new genetic features.

Specialized Transduction

When a bacteriophage transfers only a subset of the bacterial genome, this is known as specialized transduction. This usually occurs with temperate phages during the lysogenic cycle, when the phage DNA integrates into the bacterial chromosome as a prophage.

Mechanism

Phage Infection and Integration: A temperate phage infects a donor bacterial cell and integrates its DNA into the bacterial chromosome (lysogeny), resulting in a prophage.
Induction: Under specific conditions, such as stress, the prophage separates from the bacterial chromosome and enters the lytic cycle. If the excision is not precise, it may contain nearby bacterial genes.
Phage Assembly: The excised phage DNA, which now contains specific bacterial genes, multiplies and forms new phage particles.
The bacterial cell lyses, releasing phages that contain both the phage and particular bacterial DNA.
Infection of Recipient Bacterium: These phages infect new bacterial cells, introducing the donor’s genes.

Steps of Bacterial Transduction

Phage Infection

Bacteriophages infect a donor bacterial cell and inject phage DNA into the host cell

Replication and Packaging

Inside the host cell, the phage DNA controls the production of new phage particles. During this process, bacterial DNA pieces may be inadvertently packed into some of the nascent phage particles.

Cell Lysis

The infected bacterial cell undergoes lysis (bursting), releasing both complete phage particles and transducing particles containing bacterial DNA.

Cell Lysis

Infection of Recipient Bacterium

The released phage particles, including transducing particles, infect new bacterial cells. The bacterial DNA transported by the transducing particles can integrate into the recipient cell’s genome via recombination, potentially introducing new genetic features into the recipient bacteria.

Example of Bacterial Transduction

Transfer of Antibiotic Resistance Genes

Bacterial transduction can contribute significantly to the spread of antibiotic resistance in bacterial populations. For example, if a bacteria with antibiotic resistance genes is infected by a bacteriophage, the genes can be integrated into the phage’s genome during replication. When the phage infects other bacteria, it can convey these resistance genes to the new hosts, resulting in the spread of antibiotic resistance among bacterial populations.

Transfer of Antibiotic Resistance Genes

Vibrio cholerae and CTX Phage

Vibrio cholerae, the bacterium that causes cholera, can undergo specific transduction via the CTX phage. The CTX phage contains genes that encode cholera toxin, a crucial virulence factor. During the lysogenic cycle, the CTX phage joins the bacterial chromosome and replicates alongside the bacterial DNA. When the prophage is encouraged to enter the lytic cycle, it excises from the bacterial chromosome, frequently transporting nearby bacterial genes. In this case, the CTX phage can carry genes encoding cholera toxin and transfer them to other Vibrio cholerae cells during subsequent infections, contributing to the virulence of the bacterium.

Vibrio cholerae and CTX Phage

Frequently Asked Question (FAQ)

What is Bacterial Transduction?

Bacterial transduction is a type of horizontal gene transfer in which bacteriophages, or viruses that infect bacteria, transport genetic material from one bacterial cell to another. This transfer of genetic material might cause genetic recombination in the receiving bacterial cell, resulting in new genetic characteristics.

What are the Steps of Bacterial Transduction?

The steps of Bacterial Transduction are:
Phage Infection
Replication and Packaging
Cell Lysis
Infection of Recipient Bacterium

Related Article

Bacitracin Susceptibility Test- Principle, Procedure, Results, Uses