Lytic cycle: During lytic cycle of phage ,disintegration of host bacterial cell occurs and the progeny virions are released.The steps involved in the lytic cycle are as follows:
(i) Adsorption : Phage (`T_(4)`) particles interact with cell wall of host(E.coli).The phage tail makes contact between the two, and tail fibres recognize the specific receptor in phages.The on bacterial surface.The lipopolysaccharides of tail fibres act as receptor in phages.The process involving the recognition of phage to bacterium is called landing.Once the contact is and base plate to the cell surfaceThis step is called pinning.
(ii) Penetration: The penetration process involves mechanical and enzymatic dogestion of the cell wall of the host.At the recognition site phage digests certain wall structure by viral enzyme(lysozyme).After pinning the tail sheath contracts(using ATP) and appears shorterand thicker.After contraction of the base plate enlarges through which DNA is injected into the cell wall without using metabolic energy.The step involving injection of DNA particle alone intothe bacterial cell is called Transfection.The empty protein coat leaving outside the cell is known as 'ghost'.
(iii) Synthesis: This step involves the degradation of bacterial chromosome, protein synthesis and DNA replication. The phage nuclei acid takes over the host biosynthetic machinery. Host DNA gets inactivated and breaks down. Phage DNA suppresses the synthesis of bacterial protein and directs the metabolism of the cell to synthesis the proteins of the phage particlesand simultaneously replication of phage DNA also takes place.
Assembly and Maturation: The DNA of the phageand protein coat are synthesized separately and are assembled to form phage particles.The process of assembling the phage particles is known as maturation.After 20 minutes of infection about 300 new phages are assembled.
(v) Release : The phage particle gets accumulated inside the host cell and are released by the lysis of the host cell wall.[OR]
