page_title: Escherichia virus T4
section_title: Adsorption and penetration
hierarchical_section_title: Escherichia virus T4 / Infection process / Reproduction / Adsorption and penetration
caption_attribution_description: English: The injection process of bacteriophage DNA into a bacterial cell
context_page_description: 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. The species was formerly named T-even bacteriophage, a name which also encompasses, among other strains, Enterobacteria phage T2, Enterobacteria phage T4 and Enterobacteria phage T6.
  Bacteriophage means to "eat bacteria", and phages are well known for being obligate intracellular parasites that reproduce within the host cell and are released when the host is destroyed by lysis. Containing about 160 genes, these virulent viruses are among the largest, most complex viruses that are known and one of the best studied model organisms. They have played a key role in the development of virology and molecular biology.
context_section_description: Just like all other viruses, T-even phages don't just randomly attach to the surface of their host; instead they "search" and bind to receptors, specific protein structures, found on the surface of the host. These receptors vary with the phage; teichoic acid, cell wall proteins and lipopolysaccharides, flagella, and pili all can serve as receptors for the phage to bind to. In order for the T-even phage to infect its host and begin its life cycle it must enter the first process of infection, adsorption of the phage to the bacterial cell. Adsorption is a value characteristic of phage-host pair and the adsorption of the phage on host cell surface is illustrated as a 2-stage process: reversible and irreversible. It involves the phages tail structure that begins when the phages tail fibers helps bind the phage to the appropriate receptor of its host. This process is reversible. One or more of the components of the base plate mediates irreversible process of binding of the phage to a bacterium.
  Penetration is also a value characteristic of phage-host infection that involves the injection of the phages genetic material inside the bacterium. Penetration of nucleic acid takes place after the irreversible adsorption phase. Mechanisms involving penetration of the phages nucleic acid are specific for each phage. This penetration mechanism can involve electrochemical membrane potential, ATP molecules, enzymatic splitting of peptidoglycan layer, or all three of these factor can be vital for the penetration of the nucleic acid inside the bacterial cell. Studies have been done on the T2 bacteriophage (T4-like phage) mechanism of penetration and it has shown that the phages tail does not penetrate inside the bacterial cell wall and penetration of this phage involves electrochemical membrane potential on the inner membrane.
caption: Diagram of the DNA injection process
exif: {}