Lytic vs Lysogenic
Viruses are infectious agents who cannot multiply on their own because they do not have a cellular structure (acellular). Since they cannot reproduce outside a living system, they are known to be ‘non-living obligate parasites’. To replicate they must enter a live cell in another organism and then start their multiplication process. The process of viral multiplication within the live cell is known as ‘replication’. There are two different viral patterns, namely Lytic cycle and Lysogenic cycle. These patterns can also be interchangeable. Some viruses show both these patterns. They first replicate with the lysogenic cycle and then switch to the lytic cycle.
Lytic Cycle
The lytic cycle is considered as the main viral replication pattern. The viruses that show lytic cycle, first enter a cell, replicate and then cause the cell to burst releasing new viruses. What happens here is, the virus injects its nucleic acids (DNA or RNA) into the host cell and next that particular gene takes over the metabolic activities of the host cell. Then it directs the host cell to produce more viral genes. These genes and proteins are assembled into mature viruses and finally the host cell bursts and releases many viruses.
Lysogenic Cycles
Some viruses first inject their nucleic acid and then integrate it with the nucleic acid of the host cell (DNA or RNA) and make it replicate as the host cell multiplies. This new set of gene is known as ‘prophage’. These types of viruses establish long term relationships with the host cell they infect. This relationship may alter the characteristics of the host cell, but it does not destroy the cell.
Lytic vs Lysogenic
• In the lytic cycle, the viral nucleic acid transcribes itself into messenger RNAs in the host cell and then directs the ribosomes in it. So here the viral nucleic acids destroy the DNA or RNA in the host cell. But, in lysogenic cycle, instead of destroying the nucleic acid of the host cell, the viral nucleic acid integrates with the DNA or RNA in the host cell.
• In the lytic cycle, the viral DNA or RNA controls the cell functions. In the lysogenic cell cycle, viral DNA or RNA makes a long term relationship with the host cell.
• The passive replication of viral DNA or RNA takes place only in the lysogenic cycle. Here, the viral DNA or RNA becomes a part of the DNA or RNA in the host cell.
• Unlike in the lysogenic cycle, viruses produce progeny phases in the lytic cycle.
• ‘Prophage’ can only be seen in the lysogenic cycle
• Unlike in the lysogenic cycle, lysis phase is present in the lytic cycle
• In the intracellular accumulation phase of the Lytic cycle, there is a combination of viral nucleic acid and structural proteins that ultimately results in viral particles. This process is not available in the lysogenic phase
• There are viral symptoms in the lytic cycle due to cell bursts. Since the lysogenic cycle starts after the viral infection, there are no such symptoms during the lysogenic cycle
• Viral DNA or RNA may remain in the host cell permanently after the lysogenic cycle is completed. Since the host cells are damaged by the viruses, there are no such remaining viral nucleic acids in the lytic cycle
• Lytic cycle takes place within a short period, unlike the lysogenic cycle.
• The lytic cycle can be seen in many virulent virus types
• Lysogenic cycle is always followed by the lytic cycle if both patterns are present in viruses
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