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The lytic cycle results in the destruction of the infected cell and its membrane. Bacteriophages that can only go through the lytic cycle are called virulent phages (in contrast to temperate phages). In the lytic cycle, the viral DNA exists as a separate free floating molecule within the bacterial cell, and replicates separately from the host ...
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]
A prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. [1] Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages.
The life cycle of lambda phages is controlled by cI and Cro proteins. The lambda phage will remain in the lysogenic state if cI proteins predominate, but will be transformed into the lytic cycle if cro proteins predominate. The cI dimer may bind to any of three operators, O R 1, O R 2, and O R 3, in the order O R 1 > O R 2 > O R 3.
Life Cycles and Host Interaction. Corynephages exhibit two primary life cycles: lytic and lysogenic. In the lytic cycle, the phage attaches to the bacterial cell, injects its DNA, and uses the cell's machinery to replicate its genome and produce new virions. This process eventually leads to the lysis of the host cell and the release of new ...
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.
In a 1945 study by Demerec and Fano, [4] T7 was used to describe one of the seven phage types (T1 to T7) that grow lytically on Escherichia coli. [5] Although all seven phages were numbered arbitrarily, phages with odd numbers, or T-odd phages, were later discovered to share morphological and biochemical features that distinguish them from T-even phages. [6]
The lytic protein, P5, is contained between the P8 nucleocapsid shell and the viral envelope. The completed phage progeny remain in the cytosol until sufficient levels of the lytic protein P5 degrade the host cell wall. The cytosol then bursts forth, disrupting the outer membrane, releasing the phage. The bacterium is killed by this lysis.