What is the Difference Between T4 and Lambda Phage

The key difference between T4 and Lambda phage is that T4 phage is a virulent phage that undergoes a lytic lifecycle, while Lambda phage is a temperate phage that undergoes a lysogenic lifecycle.

Bacteriophages are bacteria infecting viruses. They infect and replicate only inside the host bacterium. Some phages undergo the lytic replicative cycle, while some undergo the lysogenic replicative cycle. T4 and Lambda phages infect Escherichia coli. Therefore, they are E. coli-infecting bacteria. Both phages have complex morphology. They are head-to-tail phages. Both T4 and Lambda phages are used as model systems in molecular biology.

CONTENTS

1. Overview and Key Difference
2. What is T4 Phage
3. What is Lambda Phage
4. Similarities – T4 and Lambda Phage
5. T4 vs Lambda Phage in Tabular Form
6. Summary – T4 vs Lambda Phage

What is T4 Phage?

T4 phage is a virus that infects E. coli. It belongs to the family Myoviridae and the subfamily Tevenviridae. It is a virulent phage that replicates via the lytic cycle. Hence, upon infection, this phage eventually kills the host bacterium. T4 bacteriophage has a double-stranded DNA genome, which is about 169 kbp long. It encodes 289 proteins. The genome of T4 is terminally redundant and consists of eukaryotic similar intron sequences. T4 bacteriophage consists of 3 genes to encode viral proteins. They are genes 39, 60, and 52.

T4 bacteriophage is a relatively large virus with dimensions of 90 nm width and 200 nm length. The tail portion of the T4 bacteriophage is hollow and contractile. Upon attachment to the bacterial cell, the virus injects its nucleic acid inside the bacterial cell. The tail is a complex structure with a high number of proteins for attachment and function. The head of the T4 phage is icosahedral, and it consists of spikes.

What is Lambda Phage?

Lambda phage is a bacteriophage that infects Eschechia coli. Other names of this virus are Escherichia phage lambda, coliphage lambda, and Escherichia virus lambda.  It is a temperate phage that replicates mainly via the lysogenic life cycle. During the lysogenic mode, lambda phage can exist as a prophage inside the bacterium without harming it. It can undergo a lytic lifecycle as well.

Similar to the T4 phage, it has a complex morphology of head-to-tail structure. It has a linear double-stranded genome. Each end of the genome is a 12 bp long overhang. The genome size of this virus is about 48 kbp, and it is smaller than the T4 phage genome. The diameter of the icosahedral protein capsid is around 55 nm. The Lambda phage head does not have spikes. The length of the fibrous tail of this virus is around 145 nm, and it is comparatively longer than the tail of the T4 phage. However, unlike the T4 phage tail, the Lambda phage tail is non-contractile. It also does not have a baseplate. This virus was discovered by Esther Lederberg in 1950.

Lambda phage has immense use as a vector in gene delivery for eukaryotic cells. It is used as a cloning vector in genomic library construction. Lambda phage vector can deliver a size of 35–50 kb of DNA. It is one of the limitations of this virus as a vector.

What are the Similarities Between T4 and Lambda Phage?

• T4 and Lambda phage are bacteria infecting viruses.
• Both infect the coli.
• Both show complex morphology having head-to-tail structures.
• They have an icosahedral-shaped head.
• They are double-stranded DNA viruses.
• Both are used as model systems/cloning vectors in molecular biological research.

What is the Difference Between T4 and Lambda Phage?

The T4 phage is a virulent bacteriophage that replicates mainly via the lytic cycle while the Lambda phage is a temperate bacteriophage that replicates mainly via the lysogenic cycle. Thus, this is the key difference between T4 and Lambda phage. Furthermore, the T4 phage belongs to the family Myoviridae, while the Lambda phage belongs to the family Siphoviridae. In addition, the T4 phage has a contractile tail region, whereas the Lambda phage has a non-contractile tail.

The following table summarizes the difference between T4 and Lambda phage.

Summary – T4 vs Lambda Phage

Bacteriophages infect bacteria. T4 phage and Lambda phage are two bacteriophages that infect E. coli. They are complex viruses that have head-to-tail structures. The T4 phage is a virulent phage. It undergoes a lytic cycle to replicate. In contrast, the Lambda phage is a temperate phage. It undergoes a lysogenic cycle to replicate. It exists as a prophage state inside the bacterium without harming it for generations. However, it can undergo a lytic cycle as well. Compared to the T4 phage, the Lambda phage is smaller and does not have a spike on the head, and has a non-contractile tail. So, this summarizes the difference between T4 and Lambda phage.

Reference:

1. Yap, Moh Lan, and Michael G Rossmann. “Structure and Function of Bacteriophage T4.” Future Microbiology, U.S. National Library of Medicine, 2014.
2. Casjens, Sherwood R, and Roger W Hendrix. “Bacteriophage Lambda: Early Pioneer and Still Relevant.” Virology, U.S. National Library of Medicine, May 2015.

Image Courtesy:

1. “T4 Bacteriophage” By Dr. Victor Padilla-Sanchez- Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Lambda EM” By ViralZone, SIB Swiss Institute of Bioinformatics: Siphoviridae. Photographer: Hans-Wolfgang Ackermann –  (CC BY 4.0) via Commons Wikimedia