What is the Difference Between Lambda Phage and M13 Phage

The main difference between lambda phage and M13 phage is that lambda phage is a large phage that contains double-stranded linear DNA, whereas M13 phage is a small phage that contains single-stranded, circular DNA.

The lambda phage and M13 phage are two types of viruses that infect bacteria. They are important as cloning vectors in genetic engineering.

Key Areas Covered

1. What is Lambda Phage
     – Definition, Structure, Function
2. What is M13 Phage
     – Definition, Structure, Function
3. Similarities Between Lambda Phage and M13 Phage
     – Outline of Common Features
4. Difference Between Lambda Phage and M13 Phage
     – Comparison of Key Differences

Key Terms

Lambda Phage, M13 Phage

What is Lambda Phage

The lambda phage is a bacterial virus that infects the bacterial species E.coli. It was first described by  Esther Lederberg in 1950. The phage particles contain capsid, tail, and tail fibers. Meanwhile, the head or the capsid contains the genome of the lambda phage. Generally, the size of the lambda phage genome is 48.5 kbp, and it contains double-stranded, linear DNA. During infection, phage particles recognize and bind to the host cell, ejecting the DNA inside the head into the cytoplasm of the host. The lambda phage undergoes a temperate life cycle in which either a lysogenic or lytic life cycle can occur.

Figure 1: Lambda Phage

Furthermore, the life cycle of the lambda phage ensures the replication and release of viral particles from the host cells. However, during the release of viral particles, cellular content is also released into the environment. But in certain conditions, viral particles replicate and assemble inside the host cell during the lysogenic pathway. Generally, it does not harm the host cell, and the lambda DNA inside the host is called prophage under this condition. Nevertheless, the mutant viral particles undergo a lytic cycle, superinfecting the lysogenic host cells.

What is M13 Phage

M13 phage is a virus that belongs to the filamentous bacteriophage family (inovirus). The genome of the M13 phage is single-stranded circular, and its size is 6407 bp. The encapsulation of the genome contains around 2700 copies of the major coat protein p8. In addition, the cap of the virus contains five copies of the four different minor coat proteins. Among them, P3 is the minor coat protein that binds to the F pilus of E. coli, the host of the M13 phage.

Figure 2: M13 Phage

Moreover, the M13 phage contains a short life cycle that can produce early progeny of the phage within 10 minutes of primary infection. The infected cells produce turbid plaques in E. coli lawns. During the replication of the M13 phage, the + strand of the viral genome enters the cytoplasm of the host in order to synthesize the – strand of the genome. This starts the transcription and translation of the viral genome. Assembly of the viral particles occurs following that.

Similarities Between Lambda Phage and M13 Phage

• Lambda phage and M13 phage are two types of viruses that infect bacteria.
• Both infect coli.
• They are important as cloning vectors in genetic engineering.
• They inject DNA into the bacterial cells.
• They replicate inside bacteria by replicating DNA and expressing proteins, forming new phages.
• Both are the most commonly used bacteriophages.

Difference Between Lambda Phage and M13 Phage

Definition

The lambda phage refers to a non-contractile-tailed phage, meaning during an infection event, it cannot ‘force’ its DNA through a bacterial cell membrane, while the M13 phage refers to a member of the family filamentous bacteriophage (inovirus).

Family

The lambda phage belongs to the family Siphoviridae while the M13 phage belongs to the family Inoviridae.

Size of the Genome

Moreover, the size of the lambda phage is 48.5 kbp, while the size of the M13 phage genome is 6.4 kbp.

Type of Genome

The lambda phage contains double-stranded linear DNA, while the M13 phage contains single-stranded, circular DNA.

Life Cycle

The lambda phage is a temperate phage that undergoes both lytic and lysogenic cycles, while the M13 phage releases without killing the bacterial cell.

Conclusion

In brief, the lambda phage and M13 phage are two types of bacteriophages that infect bacterial cells. Therefore, they are important as cloning vectors in genetic engineering. Generally, lambda phage contains a double-stranded circular genome of size 48.5 kbp. It is a temperate phage undergoing both lytic and lysogenic cycles in its life cycle. In comparison, the M13 phage contains a 6.4 kbp-sized genome. It is a single-stranded genome that is circular. However, M13 phages replicate inside the cell without killing it. Therefore, the main difference between lambda phage and M13 phage is the size and the life cycle.

References:

1. Casjens SR, Hendrix RW. “Bacteriophage lambda: Early pioneer and still relevant.” Virology. 2015 May;479-480:310-30. doi: 10.1016/j.virol.2015.02.010. Epub 2015 Mar 3. PMID: 25742714; PMCID: PMC4424060.
2. “M13 bacteriophage.” Bionity.

Image Courtesy:

1. “Lambda EM” By Viralzone – Own work (CC BY 4.0) via Commons Wikimedia
2. “M13B” By J3D3 – Own Work (CC BY-SA 3.0) via Commons Wikimedia