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Lysogens can remain in the lysogenic cycle for many generations but can switch to the lytic cycle at any time via a process known as induction. [8] During induction, prophage DNA is excised from the bacterial genome and is transcribed and translated to make coat proteins for the virus and regulate lytic growth. [8] Lysogenic Cycle [9]
English: Lysogenic Cycle: 1. The prokaryotic cell is shown with its DNA which is shown in green. 2. The bacteriophage attaches and releases its DNA, shown in red, into the prokaryotic cell. 3. The phage DNA then moves through the cell to the host’s DNA. 4. The phage DNA integrates itself into the host cell's DNA, creating prophage.
The lytic pathway causes the host to produce and release progeny virions, usually killing it in the process. The lysogenic pathway involves the virus inserting itself into the bacterium's chromosome. At a later stage, the viral genome is activated, and it continues along the lytic pathway of producing and releasing progeny virions.
A lysogen or lysogenic bacteria is a bacterial cell that can produce and transfer the ability to produce a phage. [1] A prophage is either integrated into the host bacteria 's chromosome or more rarely exists as a stable plasmid within the host cell.
Infection begins when the gp9 tailspike of the P22 phage binds to the O-antigen lipopolysaccharide on the surface of Salmonella typhimurium host. [1] The virion's tail fiber protein has endorhamnosidase activity, which cleaves the O-antigen chain. [3] Upon infection, P22 can enter either a lytic or lysogenic growth pathway. [1]
If so, CI represses the early promoters and the infection is shunted into the lysogenic pathway. N is an anti-termination factor that is needed for the transcription of the delayed early genes. Delayed early genes: These include the replication genes O and P and also Q , which encodes the anti-terminator responsible for transcription of all the ...
At this point they initiate the reproductive cycle, resulting in lysis of the host cell. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is replicated in all offspring of the cell. An example of a bacteriophage known to follow the lysogenic cycle and the lytic cycle is the phage lambda of E. coli. [53]
Lambda phage is a non-contractile tailed phage, meaning during an infection event it cannot 'force' its DNA through a bacterial cell membrane. It must instead use an existing pathway to invade the host cell, having evolved the tip of its tail to interact with a specific pore to allow entry of its DNA to the hosts.