Lytic cycle of viruses
The lytic cycle is so named because the cell infected by a virus dies by rupture (lysis in Greek), when the new viral copies are released. The lytic cycle is the main method of viral reproduction and involves the destruction of infected cells. The lithic cycle consists of the following phases:
- Fixation or adsorption.
- Penetration.
- Eclipse phase (replication and synthesis of viral components).
- Assembly of new viruses.
- Lysis or release.
Fixation or adsorption phase
The virus binds to the host cell stably. The binding is specific, since the virus recognizes protein, lipoprotein or glycoprotein molecular complexes, present in cell membranes, which act as receptors that allow the adhesion of virions.
In the binding or adsorption phase, the virus binds to the host cell surface. Proteins in the capsid (or envelope or caudal fibers) bind to receptors on the host cell.
The fixation in the bacteriophages is carried out through the tips of the caudal fibers by means of chemical bonds and then, mechanically, they drive the spines into the bacterial wall.
Other viruses, especially plants, do not attach to specific sites in the cell, but take advantage of areas of rupture or wounds to penetrate, or by the action of transmitting arthropods, mainly insects.