The lytic cycle is a viral replication process that results in the destruction of the host cell. It involves five distinct stages:
1. Attachment
The virus begins by attaching to the surface of a host cell. This attachment is highly specific, meaning that a virus can only attach to certain types of cells. For example, the HIV virus can only attach to cells that have the CD4 receptor.
2. Entry
Once attached, the virus enters the host cell. This can happen in several ways, including:
- Fusion: The viral envelope fuses with the host cell membrane, releasing the virus's genetic material into the cytoplasm.
- Endocytosis: The host cell engulfs the virus, forming a vesicle that transports the virus into the cytoplasm.
- Injection: The virus injects its genetic material directly into the host cell.
3. Replication
Once inside the host cell, the virus uses the host cell's machinery to replicate its genetic material and produce new viral proteins. This stage involves:
- Transcription: The viral DNA or RNA is transcribed into mRNA.
- Translation: The mRNA is translated into viral proteins.
- Replication: The viral genetic material is copied, producing new viral genomes.
4. Assembly
The newly synthesized viral proteins and genetic material are assembled into new viral particles. This process can vary depending on the type of virus.
5. Release
The newly assembled viral particles are released from the host cell. This can happen through:
- Lysis: The host cell bursts, releasing the viral particles.
- Budding: The viral particles bud from the host cell membrane, acquiring an envelope.
Examples:
- Bacteriophages: These viruses infect bacteria and often use the lytic cycle.
- Influenza virus: This virus infects human cells and uses the lytic cycle to replicate and spread.
Practical Insights:
- The lytic cycle is responsible for many viral diseases, including the common cold, influenza, and HIV/AIDS.
- Understanding the lytic cycle is crucial for developing antiviral drugs and vaccines.
