Bacteriophage Vectors
Bacteriophages are basically bacterial viruses (eaters of bacteria), and they usually consist out of DNA genome enclosed in a protein head, also known as capsid, made out of protein icosahedral (except in filamentous phages; their genetic material is not encapsulated by proteins). They do not exist as free-living organisms and they depend on bacteria for their propagation. Vectors based on the viruses are called bacteriophage vectors. There are three types of them based on the structure:
- Bacteriophages with both head and tail
- Bacteriophages with only head
- Filamentous bacteriophages
Their genetic material can be either double stranded or single stranded DNA or RNA, even though cases where genetic material is based on RNA are rare. Their genomes usually represent 50% of the whole weight. Adsorption is the term used for the attachment of the virus to the surface of the cell which results in the viral DNA being injected into the cell.
Bacteriophages can also be divided based on the lifecycle:
- Virulent – exhibit lytic cycle
- Temperament – exhibit lysogenic cycle, even though they can sometimes shift to lytic cycle
During the lytic cycle, there is no integration of viral genome into the bacterial genome. Instead, the viral genome replicates independently, host cell’s genome degrades and the cell eventually dies producing additional phages.
During the lysogenic cycle, after the adsorption, the virus inserts its DNA into the cell and integrates itself into the host cell’s genome, becoming a prophage (inactive virus, integrated into another genome). This allows for the normal replication of the host cell to happen.
Cycle that is going to occur depends on the nutritional and bacterial metabolism state as well as on the MOI (multiplicity of infection), which is basically the ratio of viruses to bacteria during the infection. Cycle change from lysogenic to lytic can also occur under certain conditions (if the cell is exposed to UV light, for example).
Bacteriophages are basically bacterial viruses (eaters of bacteria), and they usually consist out of DNA genome enclosed in a protein head, also known as capsid, made out of protein icosahedral (except in filamentous phages; their genetic material is not encapsulated by proteins). They do not exist as free-living organisms and they depend on bacteria for their propagation. Vectors based on the viruses are called bacteriophage vectors. There are three types of them based on the structure:
- Bacteriophages with both head and tail
- Bacteriophages with only head
- Filamentous bacteriophages
Their genetic material can be either double stranded or single stranded DNA or RNA, even though cases where genetic material is based on RNA are rare. Their genomes usually represent 50% of the whole weight. Adsorption is the term used for the attachment of the virus to the surface of the cell which results in the viral DNA being injected into the cell.
Bacteriophages can also be divided based on the lifecycle:
- Virulent – exhibit lytic cycle
- Temperament – exhibit lysogenic cycle, even though they can sometimes shift to lytic cycle
During the lytic cycle, there is no integration of viral genome into the bacterial genome. Instead, the viral genome replicates independently, host cell’s genome degrades and the cell eventually dies producing additional phages.
During the lysogenic cycle, after the adsorption, the virus inserts its DNA into the cell and integrates itself into the host cell’s genome, becoming a prophage (inactive virus, integrated into another genome). This allows for the normal replication of the host cell to happen.
Cycle that is going to occur depends on the nutritional and bacterial metabolism state as well as on the MOI (multiplicity of infection), which is basically the ratio of viruses to bacteria during the infection. Cycle change from lysogenic to lytic can also occur under certain conditions (if the cell is exposed to UV light, for example).
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