Lysogenic Cycle

Lysogenic Cycle

• Replication mode in viruses where viral DNA is replicated using the host's cellular machinery
• Viral DNA is replicated along with the host cellular DNA during host cell division
• Viruses benefit from the host cell replication machinery not distinguishing between the viral and host DNA

Lytic Cycle

• Another mode of viral replication where viral proteins are translated using host cellular processes
• Viral proteins are assembled into new virus particles and released, killing the host cell
• One lytic cycle can produce millions of virions, leading to high infectivity rates of viral diseases

Lytic vs Lysogenic Cycle

• In the lytic cycle, the virus takes over the host's systems, directs them for new virus production, and kills the host cell
• In the lysogenic cycle, the virus replicates along with the host genome without killing the host
• Lysogenic viruses integrate their genome into the host genome, forming a prophage
• Lytic cycle results in the production of new virus particles, while lysogenic cycle ends with the virus as a prophage

Bacteriophage Replication Cycle

• Bacteriophages are viruses that infect bacteria to complete their life cycle
• Discovered in 1915 by Frederick William Twort and confirmed by Felix D. Herelle in 1917
• Bacteriophages replicate in bacteria through the lytic or lysogenic cycle

Bacteriophage Structure

• Consists of a capsid head enclosing the genome, elongated sheath/tail, and tail fibers attached to the base plate
• Capsid proteins recognize specific receptors on the bacterial cell wall for attachment
• Can have different types of nucleic acid genomes (DNA or RNA) and sheath structures

Lysogenic Life Cycle

• Also known as a temperate or non-virulent infection where the phage establishes a dormant or latent stage
• Example is lambda phage, where the phage genome integrates into the bacterial chromosome
• The integrated phage genome is called a prophage, and the bacterial host is known as a lysogen

Lytic Life Cycle

• Also called a virulent phage, where the phage takes control of the host cell, replicates, and kills the host
• Steps include attachment, penetration, replication, maturation, and cell lysis to release new phages
• Results in the death of the host bacterium by bursting

Transition from Lysogenic to Lytic

• The lysogenic state can transition to the lytic cycle under certain conditions like UV light exposure or nutritional stresses
• Triggering this transition is known as induction, leading to the excision of the prophage and initiation of the lytic process

Lysogenic Conversion

• During the lysogenic cycle, specific genes from the prophage can lead to phenotypical changes in the host bacteria
• Known as lysogenic conversion, this can give rise to enhanced virulence or additional traits in the host bacteria

Lysogenic Cycle

• Replication mode in viruses where viral DNA is replicated using the host's cellular machinery
• Viral DNA is replicated along with the host cellular DNA during host cell division
• Viruses benefit from the host cell replication machinery not distinguishing between the viral and host DNA

Lytic Cycle

• Another mode of viral replication where viral proteins are translated using host cellular processes
• Viral proteins are assembled into new virus particles and released, killing the host cell
• One lytic cycle can produce millions of virions, leading to high infectivity rates of viral diseases

Lytic vs Lysogenic Cycle

• In the lytic cycle, the virus takes over the host's systems, directs them for new virus production, and kills the host cell
• In the lysogenic cycle, the virus replicates along with the host genome without killing the host
• Lysogenic viruses integrate their genome into the host genome, forming a prophage
• Lytic cycle results in the production of new virus particles, while lysogenic cycle ends with the virus as a prophage

Bacteriophage Replication Cycle

• Bacteriophages are viruses that infect bacteria to complete their life cycle
• Discovered in 1915 by Frederick William Twort and confirmed by Felix D. Herelle in 1917
• Bacteriophages replicate in bacteria through the lytic or lysogenic cycle

Bacteriophage Structure

• Consists of a capsid head enclosing the genome, elongated sheath/tail, and tail fibers attached to the base plate
• Capsid proteins recognize specific receptors on the bacterial cell wall for attachment
• Can have different types of nucleic acid genomes (DNA or RNA) and sheath structures

Lysogenic Life Cycle

• Also known as a temperate or non-virulent infection where the phage establishes a dormant or latent stage
• Example is lambda phage, where the phage genome integrates into the bacterial chromosome
• The integrated phage genome is called a prophage, and the bacterial host is known as a lysogen

Lytic Life Cycle

• Also called a virulent phage, where the phage takes control of the host cell, replicates, and kills the host
• Steps include attachment, penetration, replication, maturation, and cell lysis to release new phages
• Results in the death of the host bacterium by bursting

Transition from Lysogenic to Lytic

• The lysogenic state can transition to the lytic cycle under certain conditions like UV light exposure or nutritional stresses
• Triggering this transition is known as induction, leading to the excision of the prophage and initiation of the lytic process

Lysogenic Conversion

• During the lysogenic cycle, specific genes from the prophage can lead to phenotypical changes in the host bacteria
• Known as lysogenic conversion, this can give rise to enhanced virulence or additional traits in the host bacteria