How does T4 bacteriophage replicate?

Bacteriophage T4 initiates DNA replication from specialized structures that form in its genome. Immediately after infection, RNA-DNA hybrids (R-loops) occur on (at least some) replication origins, with the annealed RNA serving as a primer for leading-strand synthesis in one direction.

How is phage DNA transmitted?

The lysogenic cycle: The phage infects a bacterium and inserts its DNA into the bacterial chromosome, allowing the phage DNA (now called a prophage) to be copied and passed on along with the cell’s own DNA.

How is the T4 genome packaged into the virus head?

(a) T4 DNA is packed longitudinally to the head–tail axis (Earnshaw et al., 1978), unlike the transverse packaging in T7 capsids (Cerritelli et al., 1997) (b). Other models shown include spiral fold (c), liquid crystal (d), and icosahedral bend (e).

How does bacteriophage T4 protect its DNA?

Phage T4 protects its DNA from the two gene encoded gmrS/gmrD (glucose modified hydroxymethylcytosine (gHMC) restriction endonuclease) (CT), of pathogenic E. coli CT596, by injecting several hundred copies of the 76 amino acid residue nuclease inhibitor, IPI*, into the infected host.

What is the structure of T4 phage?

The bacteriophage T4 capsid is an elongated icosahedron, 120 nm long and 86 nm wide, and is built with three essential proteins; gp23*, which forms the hexagonal capsid lattice, gp24*, which forms pentamers at eleven of the twelve vertices, and gp20, which forms the unique dodecameric portal vertex through which DNA …

Is T4 phage lytic or lysogenic?

T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle. The T4 Phage initiates an E. coli infection by recognizing cell surface receptors of the host with its long tail fibers (LTF).

What part of the bacteriophage actually enters the host cell?

The nucleic acid of bacteriophages enters the host cell naked, leaving the capsid outside the cell. Plant and animal viruses can enter through endocytosis, in which the cell membrane surrounds and engulfs the entire virus.

How is the replication cycle of lambda phage different from that of T4?

How is the replication cycle of lambda phage different from that of T4? The genome of lambda phage can integrate in the bacterial genome and replicate in concert with the bacterial DNA. T4 can not do this but undergoes a replication cycle that results in cell lysis.

Where does T4 bacteriophage come from?

Escherichia virus T4 is a species of bacteriophages that infect Escherichia coli bacteria. It is a double-stranded DNA virus in the subfamily Tevenvirinae from the family Myoviridae. T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle.

What does T4 phage do?

The virus bacteriophage T4 infects the bacterium Escherichia coli using an intriguing nanoscale injection machinery that employs a contractile tail. The injection machinery is responsible for recognizing and puncturing the bacterial host and transferring the viral genome into the host during infection.

Why it is called T4 phage?

T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle. The species was formerly named T-even bacteriophage, a name which also encompasses, among other strains (or isolates), Enterobacteria phage T2, Enterobacteria phage T4 and Enterobacteria phage T6.

What part of the T4 phage attaches to the E coli cell wall?

coli cell. T4 attaches to an outer membrane porin protein, ompC. Immediately after injection of the viral DNA there is a process initiated called synthesis of early proteins.

What is the structure of bacteriophage T4?

For example, bacteriophage T4 of Escherichia coli has an icosahedral head structure made of repeat protein sub-units known as the capsid. This head structure contains a linear double-stranded viral genome. Phage genome varies in size from approximately 2 to 200 kilobases per strand of nucleic acid.

What is the difference between T4 and P1 phage?

The T4 genome is 172 kb, while P1 is a smaller phage with a genome of 90kb. The T4 capsid is an elongated icosahedron. T4 has a very elaborate tail structure including a collar at the base of the head and a rigid tail core surrounded by a contractile sheath. The core and sheath are attached to a hexagonal base plate.

How does DNA enter the cell wall of a virus?

Tail sheath contracts, hollow tube (core) penetrate the weakened cell wall and come in contact with the cell membrane. Viral DNA moves from the head via the tube to the bacterial cytoplasm while the phage capsid remains outside.

What is the difference between transduction and integration in phages?

During integration into host genes, the phage loses genes required for replication, this prevents the induction of the lytic cycle and killing of host bacteria. Transduction is the process by which the DNA is mobilized between cell by a virus.