User:DohaShilleh/sandbox

Lytic Cycle

Virulent bacteriophages multiply in their bacterial host immediately after entry. After the number of progeny phages reach a certain amount, they cause the host to lyse or break down, therefore they would be released and infect new host cells. The process of host lyses and release is called the lytic cycle. Lytic cycle is a cycle of viral reproduction that involves the destruction of the infected cell and its membrane. This cycle involves a virus that overtakes the host cell and its machinery to reproduce. Therefore, the virus must go through 5 stages inorder to reproduce and infect the host cell. Such stages are Attachment, Penetration, Biosynthesis, Maturation, and then Release.

Attachment

Attachment occurs when the bacteria and the phage particles come in contact. This actually happens when the attachment site found on the viral surface attaches to the complementary receptor site on the bacteria. Attachment is supported by weak chemical bonds between the attachment and the receptor site. Also, the fibers at the end of the T even bacteriophage tail plays a role in the attachment site. Therefore, there must be specific recetor attachment as the receptor determines the host preference.

Penetration

This stage involves for the virus to penetrate itself in the host cell. It does so by injecting its DNA into the cell. The process of penetration happens when the bacteriophage's tail secretes the enzyme lysozyme, which breaks down the bacterial cell wall into segments. Therefore, the break down of the cell by the enzyme lysozyme forms a hole on the host cell;so, the bacteriophage inserts the DNA (genetic material) within the cell as the capsid is kept outside the cell.

Biosynthesis

After the bacterial DNA is inserted into the cell, the process of biosynthesis is initiated. Biosynthesis involves the utilization of the host cells' nucleotides and enzymes to make copies of the phage DNA. The mRNA in the cytoplasm are transcribed from the phage DNA being involved in the biosynthesis of phage enzymes and and capsids proteins. Therefore, the ribosomes, enzymes, and amino acids of the host are involved in translation.

Maturation

Maturation is submitted by the assembly of bacteriophage DNA and capsids into virions. Late proteins are important in assembly. Assembly is complicated but varies in bacteriophage stages, some are assembled in nucleus and some are assembled in cytoplasm ,and may be seen as paracrystalline structures in cell.The tails and heads of the T even bacteriophage are assembled from protein subunits, and the head is packed with DNA and attached to the tail.

Release

The final step in viral reproduction and multiplication is determined by the release of virions from the host cell. The release of the virions occurs after the breakage of the bacterial plasma membrane. Nonenveloped viruses lyse the host cell which is characterized by viral proteins attacking the peptidoglycan or membrane. The lysis of the bacteria occurs when the capsids inside the cell release the enzyme lysozyme which break down the cell wall. The released bacteriophages infect other cells, and the viral multiplication cycle is repeated within those cells.